B..
Keep it to yourself. She doesn't need to know about your sadness. Why are you making this about YOU? Be there for her, and keep it quiet. You don't actually know anything about their marriage. I wouldn't be surprised if he was like this behind closed doors since the beginning. You can't assume he was just a sweet little man that went wrong. Ya know?
I don't really understand where you are coming from. If my friend had the guts to leave and abusive and controlling marriage, I would be HAPPY for her. She can finally leave and live a peaceful life and go on to find someone who adores her. You can feel whatever you want, I just don't understand it.
ETA: Are you reading my answer? I never said you were wanting her to go back to him!! I never even eluded to that. You are taking my answer REALLY personally, and it was in no way personal. Take a breath.