Julie was once a university student living in Texas. In 2003, she reported a sexual assault, during which she was severely beaten, but the police's handling of the investigation was sub-par. She later volunteered at a foster care facility that housed Adam Jackson, whom she met and befriended, bonding with him over their similar backgrounds, as Adam was severely abused by his stepfather. Adam came to look up to her as a surrogate mother. When she graduated and became the manager of the Hudson Street Hotel at South Padre Island, Julie got Adam a job at the hotel as part of its maintenance staff, as well as permanent residency. When Adam was jailed on two occasions, Julie bailed him out, and possibly helped acquire drugs to help counteract his severe migraines.
In the episode, after Adam, under the influence of a sadistic alternate personality called "Amanda", murdered two men at the hotel in a three-day span, Julie personally greets the BAU, who are called in to investigate. After another victim is found dead at a different hotel, the BAU deduce the unsub is likely an employee at Hudson Street and theorizes that a killing team (a dominant male and a submissive female) was responsible for the murders. After narrowing down Adam from a list of suspects for the dominant male, the BAU observe his submissive nature and believe Julie is the dominant partner of the killing team, later bringing her into their custody as she seduces a man at a bar. She and Adam later pass a polygraph test, and afterward, she watches as Adam stares tauntingly at Reid, the Amanda personality having taken over for a brief moment, and becomes suspicious.
Upon returning to the hotel, Julie sends Adam off to work, pretending that she needs to rest. When he leaves, she investigates his room and discovers a number of mirrors sheathed by a fabric cloth, as well as several items belonging to the victims. Julie goes up to the roof and confronts Adam, pleading him to turn himself in despite his protests. When she tells him she will go to the police alone, the Amanda personality surfaces, tells her "Adam doesn't need you anymore", and throws her off the rooftop, critically wounding her. She was last seen being attended to by Hotch and Prentiss after several party-goers find her. Judging by the height she fell from, it is likely Julie survived her injuries.