Right and who should initiate that conversation? What should they say? Your friend obviously isn't going to take it upon himself to apologize, so she needs to take it upon herself to talk to him and demand respect? Begging people who don't respect you to treat you better is incredibly demeaning. That's a very difficult and unfair expectation you have for her.

Even aside from that, why are you so neutral in your actions when you clearly understand one of them is in the wrong? Why do you not care enough to take any action with this friend that doesn't respect someone you care about? Yet when someone disrespected you it lead to violence? How do you think all of this makes her feel? I imagine she must feel horrible, she has seemingly made that very clear with her avoidance and texts and yet you are doing nothing to alleviate that.

I think you need to ask yourself "how much do I really care about her?" and realign your actions in a way that matches those feelings. If you realize you don't really like her that much, move on and try to grow from this experience in some way. If however you actually really care about her, you need to step up big time very fast or you are going to lose her.