What would you do if you were his girlfriend??!?

I don't blame you for giving her a shot to the face. She was a jerk. Honestly though, don't let them have that control over you. People like that are looking for a reaction from you. Be the bigger person and just walk away next time. If she would press charges, your whole future could be messed up. Companies today won't even consider hiring you if you have a criminal record. It's not worth it and she's definitely not worth the trouble.