Kelly began working for the president at an unknown time. She was considered trustworthy. After Jefferson's wife died, he and Kelly began an intimate and sexual relationship.
When Lucifer possesses the president, Kelly unknowingly takes the archangel to her bed thinking he's her lover. While lying in bed, she explains to "Jeff" that she finds the secret nature of their relationship exciting, but she wishes she could be open about their feelings for each other, but knowing the public would disapprove, they are forced to stay quiet.
Kelly believes Jeff is still lonely after the death of his wife and Kelly respects that, but she hopes that one day the two of them could get married and have a baby. She also believes that Jeff truly loves her.
When Kelly suggests Jeff would make a great father, Lucifer is inspired to have a child with her and they sleep together a second time. After Kelly becomes pregnant, Lucifer expresses his delight, happy to have created something. Kelly is noticeably disturbed by his behavior and she realizes the president is acting strange, but she brushes it off as a result from stress.
Sam, Dean, Castiel, Rowena and Crowley eventually arrive at her location to inform her of the truth, that her unborn child is the spawn of the Devil, not the president. They convince her to lure Lucifer to her location. Once the president has arrived and the guards confirm the room is secure, Kelly informs Lucifer that she can't have his child, prompting Lucifer to choke her and insist that she does. Just then, the gang ambushes Lucifer, having fooled the guards into thinking no one was there.
After they successfully banish Lucifer, the gang urge Kelly to leave. Castiel escorts Kelly to a diner, where she manages to trick him into letting her go to the restroom, from where she escapes and enters a cab. She calls Castiel to inform him that, as the child's mother, she can't bring herself to get rid of it. She hangs up, leaving Castiel in a panicked state.
Her disappearance sparks concern for the Secret Service, with Rick reporting that he isn't sure whether she is alive or not. Castiel begins tracking her down soon after.
Kelly reappears at another diner a few months later with her pregnancy visible. She is low on cash but manages to order fruit juice from the waitress who approaches her table. That night, Kelly is confronted by the waitress and an unnamed man, who reveal themselves to be angels. Before they can harm Kelly, Dagon arrives and rescues Kelly from the Angels. Dagon takes Kelly to a warehouse and offers to protect both Kelly and her child, revealing at the same time that the unborn child is a boy. Kelly ultimately agrees.When Kelly begins experiencing "weird little pains", she insists on having her baby checked out, so Dagon takes Kelly to see Dr. Turner. The doctor informs Kelly that everything is fine. To ensure Kelly cannot be traced, Dagon orders her subordinate to kill the doctor. Dagon also goes on a shopping run to purchase supplements recommended by Dr. Turner.
While awaiting Dagon's return, Kelly receives a call urging her to return to the doctor. The call is a trap and she is subsequently captured by Dean Winchester. Dean and Sam intend to take her back to the Bunker, while Mick Davies argues that the baby is too dangerous to let live. Just then, Dagon arrives and attacks the group, and retrieves a reluctant Kelly.
At their hideout, Dagon handcuffs Kelly to a bedpost out of distrust and informs Kelly that giving birth to a Nephilim is fatal to the mother, meaning that Kelly herself is going to die. This is why Kelly was suffering from pain, and it was only the beginning of what she is going to experience.
In The Future, Castiel and the angels raid Kelly's hideout and Castiel succeeds in retrieving Kelly. Castiel has orders from Heaven to take Kelly to the Heavenly Portal which will kill both Kelly and her child. Kelly insists that her child, despite his enormous strength, can learn to do good for the world, though Castiel expresses doubt, saying he can't take the chance.
Castiel and Kelly arrive at a motel. Here, Kelly reveals her attempt at suicide by slitting her wrists. She tells Castiel that her baby saved her by bringing her back to life. This is why she believes there is a purpose for her, that after all the suffering she's going through to carry the child, everything will turn out okay. Kelly places Castiel's hand on her belly and the two senses the child kicking.
However, Kelly's eyes flash gold, indicating possession by her own child. Once they are back outside, Kelly decides to go the Heavenly Portal because it is what her baby told her to do. Once there, Dagon arrives and kills Joshua, but before she can take Kelly away, Kelly's child reacts by empowering Castiel and helping him fight and kill Dagon. Castiel then drives off with Kelly, his faith in the child renewed due to visions of the future given to him.
In All Along the Watchtower, Castiel relocates Kelly to a lake-side house which the two heavily decorate in preparation for the baby's birth. Kelly records a video for her son to watch, promising him that angels are watching over him. Shortly before she goes into labor, Sam and Dean arrive at their location with their mother Mary in tow. Sam and Dean recruit Castiel in dealing with Lucifer, who has come to collect the child. Mary, meanwhile, stays by Kelly's side during the delivery.
Kelly suffers great pain before golden light travels up her body. As she glows, Kelly goes still. In her last breath, she tells her son that she loves him, and a bright light erupts between her and Mary as the baby is born.
Sam returns to house soon after to find Kelly lying dead on her bed. Sam closes her eyes and walks away, feeling remorse over her death. Sam finds out that Kelly's son, whom she named Jack, had walked over to the nursery and is now a fully grown man.
Kelly: Something happened to me, Castiel. I lost hope. I tried - I killed myself. I slit my wrists. I died. And then...he saved me. He brought me back to life. [...] His power his soul surged through me, and it was good. Pure. I feel I know he is good.
— Kelly and Castiel about Kelly's child
in The Future
Kelly was an ordinary woman with dreams for a life with a husband and a child. At some point, she became romantically involved with Jefferson Rooney, whom she wished she could openly be with instead of secretly. She trusted Jeff very much, so much that she did not suspect it when Jeff became possessed and it was Lucifer who slept with her.
Her subsequent pregnancy would alert the Winchesters to her, and cause her to learn about angels and demons. Although made fully aware of Lucifer's deception and was willing to lure him into a trap, she did not feel the same way about her potentially evil child. Despite the dangers, Kelly chose to keep the pregnancy and has shown great concern over the baby's well being, possibly the result of Kelly's former desire to have a normal family-orientated life.
Her love for her child can prove to be a weakness, as Kelly was alright with staying by Dagon's side for the child's sake, and she was easily lured back to a clinic by Sam out of fear her unborn child needed help. However, Kelly began having doubts once she learned delivering the child was fatal and Dagon's own words convincing her that the baby was going to wreak havoc on the world. Kelly's doubts drove her to commit suicide, since she could no longer risk unleashing great evil and apologized to the baby for what she was about to do.
The baby refused to die however, and subsequently resurrected and healed his mother, allowing Kelly to feel her baby's essence and realize, with great certainty, that her baby was pure. Her newfound trust in her baby drove her to trust visions delivered from the child and to insist that her baby truly had a chance of bringing the world back on its feet, rather than destroying it. Kelly even came to believe that all her suffering was not for naught, that there was a purpose behind it all.
In her final moments, Kelly was driven by the love for her unborn son, whom she named "Jack". She painted his nursery and made him a video, and openly wished for his safety and well being. She died thinking only of him.
- Season 12
- Kelly is the first and only known woman to become pregnant by an archangel.
- She is also the first woman confirmed to be the parent of a Nephilim.
- She is the second-known woman to be in a romantic relationship with an archangel, the first is Kali, who was Gabriel's lover.
- She has been called Rosemary by various characters. In pop culture, it's a reference to the film Rosemary's Baby, which is a movie about a woman that was also pregnant with Lucifer's child.