She is the mother of Cheryl and the late Jason Blossom, as well as the wife of the deceased Cliff Blossom. She is also the grandmother of the soon to be born twin babies of Jason and Polly.
She suffered severe third degree burns when running back into Thornhill to save the family portrait after Cheryl set fire to the house in an effort to "start over" with a clean slate. This gave Cheryl the opportunity to control her mother the same way she controlled and abused Cheryl.
Upon being alerted of the death of her son, Jason, she and Clifford joined the local authorities in retrieving their daughter, Cheryl, who had also been involved in the accident, from the edge of Sweetwater River. She attempted to calm Cliff down as he became verbally aggressive towards the police as they failed to find her son, despite dragging the river. Eventually, Jason's body washed up on the shores of Sweetwater and she and Cliff were forced to stand aside as their son's body was taken to the ambulance and as the body bag passed her, Penelope reached out to her son.
Penelope, Cliff and Cheryl were brought down to the morgue in order to identify Jason's body. As the cloth was pulled off his head, both Penelope and Cheryl turned away in horror. In spite of all that has happened, she and Cliff decide to attend the football game, they sat in the front row of the bleachers during the pep-rally as Mayor McCoy dedicated the night's event to the memory of Jason. Shortly after the performance of the River Vixens and Josie and the Pussycats, she became concerned as Cheryl ran off the stage in tears.
Penelope and Cliff interrupted Sheriff Keller's interrogation of Cheryl in a state of anger, Cliff demanded to know why his daughter is a suspect in his son's murder case. As they rushed Cheryl out of the office, Penelope asked why Cheryl didn't contact them, yet she did not answer and her silence spoke volumes. Despite the recent tragedy, the couple decided to attend the first annual Taste of Riverdale event, in which Penelope had a brief, but violent run-in with Alice Cooper. Penelope slapped Alice on sight, appalled that she would dare print Jason's autopsy in the Register.
The Blossoms were interviewed by Sheriff Keller as he continued his investigation of Jason's death. Everyone in town had their own suspicions, neighbor suspecting neighbor. During which time, Riverdale bared a striking resemblance to Salem, during the witch trials.
Investigating Jason's Death
Penelope stood in the doorway of Jason's room, where she watched Cheryl while she slept in his bed. As her daughter awakened, she told her there would be no more sleeping in Jason's bed. Cheryl explained that she dozed off while working on the eulogy, unfortunately, Penelope abruptly put an end to that, she told Cheryl that she would not be allowed to speak at Jason's memorial, as she would only run the risk of embarrassing the family.
The next day, Penelope led Sheriff Keller into the room in which Jason's memorial would be held, afterward, they would bury him in the cemetery on Thornhill ground. She then informed the sheriff of the list that she and Cliff composed, which consisted of all suspects in the murder of Jason, she believed there was a very strong possibility that the killer would be in the room for Jason's memorial.
That night, the Blossom family ate dinner together, they were joined by Veronica Lodge, Cheryl invited her, yet Penelope has no idea why. Cheryl commented on the subject of her being prevented from speaking at Jason's memorial, which caused Penelope to remind her that she already said her goodbyes to Jason, when she rowed him over Sweetwater River, to his death.
The day of the memorial, Penelope stood by the door, greeting each guest as they entered, when face to face with Hermione Lodge, things took a nasty turn, she accused Hermione of being happy over Jason's death. Before the service began, Archie Andrews approached her, offering the family Jason's old jersey from his time on the Riverdale Bulldogs, she couldn't help but notice the similarities between Archie and Jason, brushing his hair back, and caressing his face, then accepting the jersey. Furious with Cheryl over her disobedience, Penelope explained to her that she'd no longer be on the River Vixens, and if not for the fact that no one wanted Cheryl, she'd be shipped off to boarding school in Europe. As planned, Penelope laid Jason to rest in the cemetery, following the memorial.
With the discovery of Jason's vehicle on route 40, Penelope went down to the Sheriff Station wondering if they were any closer to solving the mystery. Cheryl then unexpectedly showed up at the station, offering a piece of information, but only if Penelope allowed her back on the River Vixens, to which she agreed. Cheryl revealed that Polly Cooper had escaped the Sisters of Quiet Mercy group home, so with Jason's vehicle being burned to a crisp, it's possible that she was the culprit of both the fire and the murder. Following the revelation of Polly Cooper's escape, the Blossom organized a witch hunt throughout Eversgreen Forest, where they had a run-in with the Coopers. Penelope informed Alice that the noose was tightening around Polly's neck, and the entire town would know it once they find her.
During the press conference held by Alice Cooper, she learned that Polly was pregnant with Jason's child. Penelope, Cliff, and Cheryl met up with Betty at Pop's Chock'lit Shoppe in order to discuss future plans with Polly and the baby. She and Clifford were relieved to learn that they were safe, Penelope wanted to offer emotional support, as well as financial. She asked where Polly was residing, but Betty refused to answer, Penelope reminded her that she and Polly were members of the Blossom family, and they'd be ferociously protected, as long as they all trusted each other.
Back at Thornhill, Penelope asked Cheryl is she had ever seen Polly take drugs, which Cheryl wasn't sure of, Penelope explained that she wouldn't want an unfit mother to raise her grandchild.
Surprisingly, even after accusing Polly Cooper of being an unfit mother, the Blossoms were still invited to her Baby Shower, being held at The Pembrooke by Hermione Lodge. Penelope began the event with an apology for embracing the child and not her, she had hoped Polly could forgive her. The gift opening portion of the night had come, and Penelope insisted that Polly opens there's next, inside was a miniature rocking horse, it was a family heirloom that great-grandfather Blossom used to play with. She and Cheryl then extended an invitation to Polly for her to stay with them at Thornhill, she and the child would want for nothing, which unsurprisingly, didn't go over well with Alice, leading to a momentary quarrel. Penelope was under the impression that Alice had disowned her daughter, considering that she as staying at the Pembrooke instead of the Cooper house.
Polly screamed at them both to stop with the non-stop hatred for one another, their constant bickering is what led to Jason's death, she claimed, simply because neither Penelope nor Alice would just allow them to be together. The next morning, she and Cliff welcomed Polly at the front door as she had accepted their invitation to stay at Thornhill.
Fall of the Blossom Empire
Thicker than blood, and more precious than oil, Riverdale's biggest trade business had been maple syrup since the founding of the town, which the Blossoms had been in control of since the beginning. Following a flashback, where Penelope, Cliff, Cheryl and Jason sipped syrup almost as if it was fine wine, the Blossoms had to address a major problem. The death of her son precipitated a crisis within their family, with Jason gone, many wondered who would inherit the family business. With that in mind, the Blossoms awaited the arrival of the board of trustees, circling the wagon against possible attack from within their own rank.
Later that day, after learning that Archie turned down Cheryl's invitation to the tree tapping ceremony, Penelope took matters into her own hands, informing Archie that she could get him into an exclusive summer music program if he escorted Cheryl. She remembered how Archie brought her Jason's Riverdale Bulldogs jersey during his memorial, an act of kindness during a moment of despair, which made Archie a decent person in her eyes. Penelope eventually managed to persuade Archie into attending the tree tapping, and in return, she'd give Great-Uncle Harrison a call at the Brandenburg Music Academy.
The next day, Penelope and Cliff were extremely nervous as Cheryl was to perform the ceremony in Jason's place, fortunately, the ceremony could not have gone better as Cheryl tapped the tree perfectly. Later that week, Penelope sat at Clifford's side as the banquet at the Belmont Lodge took place. Outside, she informed her husband that while the trustees appeared to be satisfied, uncle Bedford kept asking about the drive-in land. Cliff promised that he would regain the land, but they never suspected that Hermione Lodge would be so resourceful. Penelope joked that maybe Cliff should have sent Hermione to prison instead of Hiram, unaware that Archie was listening in.
As the trustees were leaving town the next day, Penelope wondered if they had been appeased but cliff assured her they weren't out of the woods just yet.
Having learned that Polly had earlier made her way to the east wing of Thornhill, where Penelope and Clifford's sleeping quarters resided, Penelope informed Polly that this specific area was off limits.
The next day, Penelope offered Polly an explanation as to why she was in possession of Nana Rose's heirloom ring, which was thought to have gone up in flames along with Jason's car. She claimed the last time Clifford saw Jason was the day he rid himself of the Blossom family, he wanted nothing more to do with the name or lineage, including the ring, which he threw in Cliff's face as a final rebuke. Cliff then gave the ring to Penelope for safekeeping. Polly was under the impression that the ring was lost, but "nothing's lost forever, everything comes back", Penelope said. She then insisted that Polly finish her milkshake, which Penelope later revealed to both Cheryl and Cliff that she had drugged with a relaxer, leaving the babies unharmed but putting Polly to sleep in the process.
Before Cheryl left for the Homecoming dance, Penelope made a point to ask her for the heirloom ring that had been taken, however, come to find out, Cheryl flushed it in anticipation that one day Polly might reveal the truth about the ring to someone, there wouldn't be any proof, simply her word against their's.
Following the arrest of FP Jones for Jason's murder, Penelope wept angrily and told her husband that she wanted FP dead for what he had done to her son. Unbeknownst to either that Cheryl was watching, Cliff held Penelope as she cried and promised to take care of him.
The very next morning, Penelope informed Polly of the latest development in Jason's case as FP Jones was arrested for his murder. Jason would finally have peace, and they could all start over.
Later that night, a loud knocking could be heard all throughout Thornhill, much to her surprise it was the Coopers, coming to take Polly back. Penelope reminded them that Polly chose to stay with them, a mentally stable family. Unfortunately, she wasn't aware that Alice was aware of the family relationship between the Blossoms and the Coopers, in which Clifford's grandfather and Hal's grandfather were brothers, thus making Polly and Jason relatives, third cousins to be exact. Betty then accused her of killing Jason to hide the fact, but it was quite the opposite, as Penelope remarked that nothing could be more purely Blossom than Polly's babies. As Betty attempted to leave, Penelope grabbed her wrist and told her that she made a grave error.
The following day, as she sat alone staring at the fireplace, Cheryl approached her with a question, asking about the fight that took place between Jason and her father on July 4th. A question that had previously been answered, they'd already told Cheryl that Jason didn't have the stomach for the family business. Cheryl believed that whatever happened to Jason involved their family, she wondered if he was running away from Clifford, or even her, which Penelope took great offence to as she firmly grasped Cheryl's hands, and dragged her to their family's barn. She pushed Cheryl inside, and told her that maple syrup was the dark truth, to "drown in it, why don't you", she said.
As she and Clifford at dinner together that night, Cheryl entered the dining room and accused him of killing Jason, and she could prove it with the video surveillance from the night Jason was killed. It wasn't long before Sheriff Keller and his deputies arrived at Thornhill, in which time Penelope and Cheryl directed them to the barn, where Cliff had hung himself. 
After the suicide of her husband, Clifford, Penelope and Cheryl stood idly by as law enforcement turned their home into a crime scene upon the discovery that Clifford killed their son after Jason found out about his drug distribution business. Following the funeral of her husband, she and Cheryl returned to the Blossom Maple Farms. She wondered why Cheryl was crying since she always hated her father. The Blossom family had always been cursed, every since brother killed brother, "who will the grim reaper take next", she said. Penelope then looked up to the rafters, where Clifford hung himself, and began wondering if he had made the right decision by ending it, better the sweet hereafter than that awful limbo.
The next day, before leaving Thornhill, she was approached by Cheryl, who requested to stay home that day, but unfortunately for Cheryl, Penelope stubbornly denied her request, as she didn't care about her struggles. Penelope later went on to attend the 75th Anniversary Jubilee at the Town Hall. She sat in the crowd as Betty Cooper gave a speech about the turmoil Riverdale was facing after the death of her son at her husband's hands. Their town was at a crossroads, and if they didn't do something to fix it, what happened to Jason wouldn't be the last.
After the Jubilee. she returned home to find a strange smell and Cheryl, who is unhinged after a failed suicide attempt, with a candlestick in her hand. When Penelope asked what the smell was, Cheryl explained that it was gasoline and that she believed the only way they could start over is to burn the house down, which she did by dropping the candles into the gasoline. The two of them quickly left outside and watched as the house burned, with Cheryl smiling, while Penelope, who is horrified and outraged at the destruction of the house, lashes out (which Cheryl ignores). 
As an aftermath of the Blossom house burning down, it was revealed that Penelope had gone back inside the house only to salvage the Blossom family portrait, suffering major third-degree burns and acute smoke inhalation in the process. However, the truth never came to surface, as Cheryl created a cover story to cover up for the fact that she burned down their home in an attempt to start over. As the story went, Cheryl was asleep after the incident at Sweetwater River, the breeze probably knocked a lit candle over, setting fire to the curtains. After Penelope returned from the Jubilee, she ran headlong into the blaze to save Cheryl, leaving her severely burned.
As Penelope was left in a critical condition on the hospital bed, bandages covering her entire body, Cheryl taunted her. Blackmailing her mother, Cheryl warned her that if she told anyone what really happened at Thornhill, she'd tell everyone about what really happened to Cliff in the barn, implying that there was a dark secret surrounding Cliff's death. When Cheryl makes it very clear that the abuse of the elder Blossoms has come to an end and that she now had control over the family, Penelope's dominance was reduced to a mere shadow of the ominous woman she once was.
Penelope is an attractive middle-aged woman with tan skin, red hair, and light brown eyes. She is of medium height and a thin build. With the Blossoms being the most wealthy family in Riverdale, it should be a surprise to no one that she dresses very classy and has expensive taste. She suffered severe third-degree burns after Cheryl burned down the Blossom house and she ran back in to save the family portrait.
Penelope is cold-hearted, manipulative, and calculating. Despite her apparent love for her son, Jason, and her husband, Clifford, Penelope seems to despise Cheryl, constantly treating her terribly, in a very unmotherly manner. Verbal abuse is a common theme in reference to Penelope's treatment of her own daughter. She's also been shown to be manipulative towards Cheryl, as well as others, such as Archie Andrews, who she bribed into escorting Cheryl to their family's tree tapping. In spite of all this, Penelope has a softer side, generally displayed whenever Jason is involved. She cried many of times following his death, as the passing of her son was too much to bear, leaving her deeply saddened.