Under no circumstances should you ever bite someone there. She could have just left, or given him a nice slap in face, or called security on him.
I'll tell you right now, here's what really happened:
This girl is drunk out of her mind at a club where everyone knows you'll get hit on if you go there because everyone is drunk out of their minds. This guy hits on her that she doesn't like, but she's too drunk to talk, so she does the logical thing that any drunk person would see as the right thing to do by biting his doo-dad.