I'm so sorry, NYCDoglvr. I was in your friend's position; my sister in yours. Neither side is easy. I know my sister stepped back when I went back to AXH the last time. Like others mentioned here, she'd touch bases once in a while to see how I was doing. She'd gently remind me that I had options. And in the little ways she could, she'd remind me that I deserved to be happy.
Like, if while we were talking I mentioned that I was confused by him not being happy that I'd gotten a promotion (the reality that I didn't tell her was that he had screamed at me about how I thought I was so much better than him, it was still JUST an office job that any stupid girl could do, that I was so dumb) she'd tell me we need to do a girl's lunch to celebrate such a great accomplishment and make plans to meet me on a work day for lunch.
I don't know if she had seen information similar to Carlotta's post, but she pretty much followed the how to be supportive line. I know it wasn't easy on her. And I know that's why she tended to restrict her visits to days when she knew AXH was working, or to days where we'd plan her swinging by and I'd head out the door with DS as soon as she pulled in the drive. To be completely honest, it was easier on my side that way, too. I caught less flack from AXH if he didn't see her or my family or friends.
I don't know if it will help clarify your friend's side any, but I wasn't letting AXH hurt me. It all started out so small, but the end result was a crushed sense of self-worth and self-confidence. I didn't know marriage could be different. SHOULD be different. I thought I was mis-communicating with him. I believed his apologies and words of love. I thought he loved me, and while some of his actions were hurtful, some of his actions seemed loving and he would either show remorse after "he was angry" or convinced me I mis-understood. I thought that if I found the right words, I could explain to him what the relationship was like from my side and since he loved me, he would change. IDK. I know that none of that made it any easier on my sister watching me fade into a shadow of myself.