At a time when she was struggling in school, Corey became convinced that her boyfriend was cheating on her and became obsessed with discovering the truth. To this end, Corey went so far as to kill her cat Mittens so that she could use her skull in a summoning spell for the Goddess of Truth Veritas.
Through Veritas' truth curse, Corey got the truth about her boyfriend's cheating, a truth that drove her to commit suicide via car accident. Aside from her roommate, no one realized that Corey's death was anything other than a simple car accident so she wasn't listed with the other four people who killed themselves starting a week later due to Veritas' truth curse, a curse Corey had unwittingly unleashed upon her hometown.
While investigating the suicides surrounding the truth curse, hunter Sam Winchester discovered that Corey's body had been taken from the morgue along with Veritas' other victims. Sam realized that Corey had most likely committed suicide as well and due to the timing of her death, was most likely connected to the source of the curse. Questioning Corey's roommate, Sam learned of Corey's obsession with finding out the truth and found her spell paraphernalia, allowing the Winchesters to identify Veritas as the being behind the curse.
Powers and Abilities
Due to her boyfriend's possible cheating, Corey developed an obsession with finding out the truth, using every means possible to get answers. These methods included summoning the Goddess of Truth Veritas and killing her own cat to perform the spell with Corey lying that her cat had run away to cover it up. After learning the extent Corey went to in order to find out the truth, Dean Winchester considered her to have gone insane instead of being just obsessed.