Audio problem: During the girls' follow-up discussion after Tracy has sex with Ravi, Evie laughs and says, "What? We didn't go over that one." However, her lips aren't moving when she speaks the second sentence; the second part was obviously dubbed in later.
Continuity mistake: When Tracy first goes to meet Evie, she gets on the bus with no purse. She even leaves her house without one. When she sees Evie in the store, she has a purse on her shoulder.
Answer: Evie was based off several people in Nikki Reed's life.