Don't freak out over her Dad, if you act all nervous and stuff he's probably going to think you're an idiot or he'll find it slightly amusing that you're trying so hard. DON'T STRESS, just be calm, she's only human and so is her Father. Yeah sure, be cautious about the fact that he is around, but remain who you are and things should run smoothly.
These guys sound like idiots, they've probably realised that their loud and obnoxious routine doesn't impress her, so they've moved onto physical abuse towards other people who are a threat, can you say insecurity?
Forget them, forget her Dad and just talk to her.
To love is to suffer. To avoid suffering, one must not love; but then one suffers from not loving. Therefore, to love is to suffer, not to love is to suffer, to suffer is to suffer. To be happy is to love; to be happy then is to suffer, but suffering makes one unhappy; therefore to be unhappy one must love or love to suffer or suffer from too much happiness. I hope you're getting this down.