Plot Question

My interpretation is that she overdosed because as we glimpse through the film, she is an addict, alcoholic (why she refuses when offered a drink and says "no thanks i don't drink" and she also discusses the things she did when she was drunk and how her parents sent her away for it) and she probably suffers from some depression or other mental illness. What I felt from watching it, was that she seemed somewhat aloof of the group, more withdrawn and introverted, and kind of stuck in her own inner turmoil and issues, trying to cope with them. I also feel like everyone around her is busy bitching, complaining, being immature and everyone is so focused on themselves that they all fail to really notice her, she just seems to be in the background (like when she disappears and sooze finally notices and asks where she is). My guess is that she overdosed because she wanted to end her pain, but also it would appear to possibly be a cry for help, her only way of knowing how to really get anyone's attention in the group, and why she decided to do it on the rooftop of the minimart, because that's where they all hang out, so someone would likely find her there. She could have went to a place where no one would find her at all, or used a more fatal and instantaneous method of suicide, but she chose the pills instead.

She seemed to also feel used by Buff who had his way with her and then started hitting on Erica right in front of her. She was clearly bothered by it.