Let's not forget that JA has been dating boys/men since she was fifteen. She's been cheated on before and walked away. She has confronted the "other" woman before. This wasn't a woman who suddenly found herself in a situation she didn't know how to handle. It wasn't as if TA could somehow take advantage of her "inexperience". She so knew what was up.
Good point. The majority of the previous boyfriends cheated on her and abused her, so she claims.