Allison Reynolds (Ally Sheedy)’s Timeline and Summary

A father who seems to ignore her entirely drops Allison off at school.
In detention, she barely says anything, but does odd things like making a sandwich with sugar cereal on it and using her dandruff as snow in a landscape drawing.
Later, she interacts with Andrew a little, asking him why he's really in detention—but he doesn't give her a straight answer.
When she and the other kids end up sitting in a circle—Allison hasn't smoked pot with Bender but the rest of them have—she lies, claiming that she's a nymphomaniac who's had sex with her psychiatrist.
This causes a chain of events in which Claire admits that she's a virgin. Allison explains that she is too, and the whole nymphomaniac thing was just one of the lies she compulsively tells.
At the end, Allison gets a makeover from Claire, changing her look entirely. She and Andrew look like they're going to be together.