>>213670322They kind of explained it on the show. Overbearing parents, especially Minh. Then she finds out they're getting divorced as soon as she goes off to college. Now she's confused, in a new town, alone, and probably easily influenced. She said she doesn't want to end up like her mother so now she's afraid of commitment. So she builds rules so she can't get hurt, but can't get close either.
Also she already was a whore even as a kid. Didn't she cheat on Bobby with his best friend as revenge?