If she's still dating the other guy, what can you do? Is she going to wait around for you to come save her and drag her away from a relationship she chooses to be in? Maybe she needs more time to completely detach herself from the guy she is dating, and if it continues at the rate it's at. Most likely he didn't learn anything and will be back to mistreating her soon, just wanted her back out of loneliness. That's just speculating, but when most relationships are broke, they are hard to fix.
She has to ultimately choose her own destiny. You aren't a completely proven guy in her mind yet no matter how much you have hit it off so she is going to be afraid. But who is she to continue to stay with somebody that mistreats her and is unhappy? I know we can be very blind in a relationship when we care about somebody, but life's a learning process and some lessons have to be learned the hard way. I don't mean to sound cruel, I'm speaking from my own personal experience as being dumped and learning it by losing her completely. The lesson sticks.
I would say if she contacts you next, you let her know how you feel but that you can't be there to support her if she wants to be with him. I know it might be difficult and you care about her but you can't really hold her hand through this. She has the best of both worlds, her comfort with her current guy and the emotional support from you. You gotta think about yourself too and what this is doing to you.
She can't possibly be mad at you for it. You will be able to find happiness with somebody else and if she decides enough is enough, guess who the first person she will talk to is? Doesn't that sound like a win-win?
Waking up next to a beautiful girl,
Step outside and say hello to my beautiful world.