Kassidi meets Carl when he takes her and others in. She points out that none of the families of the group he has taken will give him money. Kassidi gives Carl the idea to send a ransom note to her wealthy father and that way he can get his money. Her father, who knows it's a scam, gives Carl the money hoping that she will come back home. Carl lets her go now that he has the money he needs, but she doesn't want to leave and begs Carl to let her stay with him. She then gives him oral sex and he allows her to stay.
They begin to fall in love and begin dating but Carl sees that she is obsessed with him.
Carl prepares to return to military school which makes Kassidi is upset. He buys her a promise ring which she mistakes as Carl proposing to her. Carl didn't want to upset her and thinks he does love her so he impulsively decides to marry her. Kassidi wants to get married right away and Carl, who doesn't want to lose her, agrees.
They are married with the Gallagher family present minus Frank Gallagher who doesn't believe Carl marrying Kassidi is a good idea. In order to stop Carl from going to military school, Kassidi handcuffs him to his bed for a day until he falls asleep. However, Carl's brother released him and Carl escapes the house.
Carl boards the bus leaving for millitary school leaving Kassidi yelling and crying to Carl, begging him to come back, Carl ignores this.
Kassidi has followed Carl to military school and set up a camp outside the fence of the school. Seeing that he was serious about school, she decided to support her husband in his endeavors by dressing up as a cheerleader and cheering for him, to his embarrassment. Kassidi still showed clinginess by counting down the days until he is let out of school and confessing her love for him. When complaining about this to his platoon, one of them who was having problems with decided to help. The cadet later told Carl that he handled it and the body won't be found, implying he killed Kassidi. There was no trace of her at the camp, as Carl became worried while the cadet was pleased.
- Carl used his phone to record him and Kassidi having sex.
- Due to her erratic mood swings, temper tantrums, black and white thinking, fear of abandonment, self-destructive behavior, and chaotic relationships with others, it’s likely she has some kind of mental illness such as Borderline Personality Disorder.