[Bring_Back_Shantz]

I know she said she'd never talk to you again but you have to ask yourself if keeping her as a friend is worth her safety.

What she thinks of you should have no bearing on your decision as her safetly is the most important issue in all of this.

If buddy is hitting his girlfriend, he deserves everything he gets.

Unfortunately this seems like a situation where the cops will show up to field a complaint, she'll refuse to press charges, he'll beat the hell out of her again, she'll storm into work and give you hell and probably never speak to you again but at least you'll have a clear conscience having at least tired to do something about it.
Unfortunately, unless this woman wants help, nothing is going to change.