My friend's situation

My friend (well ex friend ) is in a very a unhealthy relationship. He controls her, shouts at her and beats her up pretty bad. 
It's not just suspicion, I've seen very aggressive behaviour from him, whilst drunk one night she admitted to it all. Once sober denied it all.
I tried being there for her as much as possible but she completely turned on me, cut me out and called me every mean name under the sun. 
I was always the person she came to when they argued (obvs once he apologied it was as if it never happened) but she's blocked me on everything and left our mutual work. 
I don't know what else I can do but it is seriously heartbreaking. Have you girls been through anything similar ? Maybe some advise? 
I'd rather keep this thread anonymous so please don't think I'm rude if I don't reply 💕