(((Joan))) - so sorry you are going through this. Your daughter is angry and she's going to have to work her way through that...or not. Hopefully, she will. I don't see it as choosing between one or another (though I'm sure she would disagree), but she is making the choice to not attend family functions when he is there.
Any chance SHE would go to al-anon? After all, she has been affected by his actions and is holding a lot of resentments.
Sorry I don't have any advice. I know that my niece and I are currently not talking because of something she did but swears it was "my fault". She, too, has a lot of anger (about her life, in general) and has chosen to take it out on me. I miss her, I love her dearly, and did send a text of support when she was staying with her best friend and the friend's mom OD'd one night (she's fine, has OD'd once since then and in treatment). I got no reply.
I've chosen to let her walk her own path. If she wants to be angry at me because of her life (and granted, she's had a tough one), then so be it. She knows I love her, and I just pray that someday she'll come around. My dad has said he feels like he has to choose between the two of us. I told him he was wrong...he can talk to Brit whenever he wants to, but I don't necessarily want to hear every time he does. I do ask if she's okay, but she rarely talks to any of us, these days.
So yeah, I kinda get where you're at and it's no fun
Hugs and prayers,
Amy