Question: Why is Darian changed to Adrian in the TV version?
Question: What sort of mental illness does Darian have? And for that matter, she seems to come from a stable home and family. Since this is the case, why should she be mentally unstable and how come her parents never noticed her condition when she was growing up?
Answer: Darian would likely be considered as a depiction of Borderline Personality Disorder. She immediately idealizes Nick, becoming emotionally attached to him, which leads to her wanting him all to herself and becoming jealous of his relationship with Amy. Nick's rejection of Darian's sexual feelings for him and his insistence that they be simple friends is what leads her to her feelings of wanting revenge, while she also has unpredictable short-lived mood swings and unreasonable anger over trivial situations. To top it off, her pettiness and lack of remorse in sabotaging Nick in ways like vandalizing his car, erasing his work, trying to harm Amy and even her closest friend, would be almost certain to lead to a comorbid diagnosis of Antisocial Personality Disorder, especially considering she didn't change in the end, and those with BPD aren't typically violent against others (as media often portrays).
Answer: I don't think Adrian was written as having a specific mental illness. Regarding her family, it's not unusual for someone with her issues to come from a stable, well-respected home. Real-life stalkers and killers have. Their families, friends, neighbors, etc. were truly shocked by what these criminals did. They knew a totally different person, compared to the person who the victims encountered.
Answer: The scriptwriter based the film on events that actually happened to him and rather unwisely didn't change the name of the girl. She sued him, hence the change of the name for the TV version.
Tailkinker ★