She grabbed his arm. He pushed her hand off (rather forcefully) and told her not to touch him. Whereupon she slapped him. Not to excuse his hitting the woman. And acknowledging that while she was slapping him repeatedly, he didn't have to retaliate. But, this is definitely drunken, trashy behavior. I would presume that her mother failed to teach her what is and is not ladylike behavior. And that a lady does not, while drunk and in public, provoke a physical altercation with a man she does not know (or one she does for that matter). Forrest Gump, life, chocolates and all that.
Edit: I take it back. She did not grab his arm first. It appears that while saying something about "getting the F out", she poked him and that's when he said "don't touch me".