No. Call the cops now. Not 911, call their 'regular'/non-emergency number and ask to talk to someone who can advise you about what can be done for your friend.
If he abuses her again (and I hope he doesn't), but YES, try one more time to get her to;
a) leave him and NOT go back. There's no good reason she can't.
b) if necessary get the cops involved.
Bottom line, SHE needs to extricate HERSELF from the situation or at the very least be a willing participant in her own well-being. If she is NOT willing to participate in her own well-being and she chooses to go back, there is just about nothing you can do without getting yourself or her in more trouble or worse.
The advice about getting tough with her and choosing to stop enabling her is to get her to realize that part of her drama cycle that she's so addicted to is about to go away. She thrives on the attention you give her. She is NOT serious about fixing her situation - at least not as serious as she is addicted to the attention she's getting from both of you. In a sense, you're as much of a part of the problem as the abusive boyfriend.
Sure, she doesn't like getting hit - but so far it hasn't killed her and the aftermath where you 'ride in on your white horse' or sympathize with her and tell her how much of a jerk he is and how she doesn't deserve such things is still a powerful draw for her.
After she gets her 'white knight' fix, her life goes dull again so she goes back for a 'black knight' fix. She may even provoke him knowing his hot buttons and how to get him to act out. I am not saying she IS - but her simply going back is a good sign that she isn't very good at making good choices - like a junkie to the needle.
He does what he does - she get's her 'black knight' fix and goes running for her 'white knight'... again...
If you let her know that you are not interested in playing a part in her negative, self-destructive behavior - that you are willing to help her if she agrees to help herself (ie: stop going back for more) - then you are done boo-hooing with her over the mess she continually puts herself into when she knows full-well how to make it stop HERSELF.
That sounds harsh because that's what 'tough love' is - harsh. But enabling her is not helping her. You playing "white knight", even in the fantasy she's creating, is only fuel for her drama addiction. He's a part of the problem - she's a part of the problem - you're a part of the problem. None of you are choosing to NOT be a part of the problem.
