I would call the cops, too, but I'd still be shocked that there are women in this day and age who LET their partners beat up on them. Hell, maybe if she'd bash his head in with a frying pan one night in his sleep, if he survived, he'd keep his mitts of of her then!
Okay, truthfully, I'm KIND OF joking as I wouldn't hit my BF in the head with a skillet (because, you know, I'd probably go to jail too and I don't want that), but I would try to hit him back or something (only in self defense, as I'd never hit a guy or any other person unprovoked), then leave and take my kids with me so as to not perpetuate the cycle of violence. But I wouldn't stand around and let some guy beat me up time after time. Forget that.
I have a client who, last week, was locked up because her and her BF got into a domestic dispute and HE called the cops on HER. Both of them went to jail, however, and I think: what a waste. They're already quite poor, and what little money they had they had to waste on bail.