What happened at the party Val went to in Don't Look Behind You?

According to Valerie—whose real name is April—she talked too much at the party and let part of her true past slip to Larry, who was angry that she lied to him.
After Amy invites Larry and Valerie to her party when they run into each other at McDonald's, he says he'll pick her up at eight. When they arrive, they find out that Amy's parents are gone. Fran, Amy, and their boyfriends make a frothy alcoholic punch that they call "Suicide."
Valerie says the punch was deceptive because it tasted like fruit juice. She was nervous because she felt out of place, so she drank to feel better. They dance and when they stop, Larry gives her another glass. She continues to drink.
Later, when she's lying on a lawn chair and thinks her boyfriend in Virginia—Steve—is kissing her, she realizes it's really Larry. She tells him to stop and that she has a boyfriend back in Virginia. Too late, she realizes this contradicts the story her family is supposed to tell people about their past. Larry argues with her, wondering what else she lied about. He says that Abby told him she was from Virginia; he doesn't even believe she's being honest about her name.
They argue and he accuses her father of being a criminal. Larry takes her home, and she throws up in the driveway before going inside.