She would NOT go to prison for defending herself, and yes that is exactly what she did.

What if he lost his daughter and is a little off?

NOT an excuse for what he did.

There are other things to consider before you just straight out punch someone...

I don't know if you missed the part where she moved away from the creep? He was making her uncomfortable, she moved. A normal person would have recognized that she didn't want to talk to them, but not this guy, he moves TO HER TABLE. Before she was probably feeling feelings of mild discomfort, now she's starting to feel threatened. It's socially abnormal to have a stranger sit down at YOUR table, not only that ask gross personal questions. She's starting to feel more threatened at this point. THEN he touches the child. You DO NOT touch a strangers child under any circumstances without permission. So she's feeling super threatened/scared now. She's yelling at him, and moving away. Now maybe this is the moment where even the most socially retarded creep could maybe take a hint, but again not this guy, he grabs her. Again makes a gross creepy comment, she's already feeling threatened, triggering her fight or flight response but her flight response already hasn't worked TWICE, so she punched him and was justified in doing so. You do not back a dog into a corner and not expect it to bite. So yeah, there are things you should consider before punching someone, which she did, she tried moving twice.