Future, I agree with Puppy that the first part would be tough to accept. Perhaps she was saying that she doesn't think it was a mistake because it "changed" her in ways she needed to grow in her life. Maybe she's not necessarily saying that the A wasn't wrong, just how it changed her? Right now these are her feelings, her emotions. She's still processing that time in her past too just as you are. That time means completely different things for you both right now.
From my observation it seems like you both pretty much agree and get along with every other issue in your sitch. It all seems to come back to the A. If you don't mind me making a suggestion, I think the two of you discussing the A on your own is not working right now. Perhaps you both could go to a MC appointment to discuss it. This might be getting to the point where only professional help might help the two of you deal with this and put it behind you both. It seems to me that when you both discuss the A things seems to fall apart. With the other positive things that you both have been able to work on it seems like this might be the final issue to resolve.
Maybe ask her if she would be willing to only discuss this issue in counseling at this time. Find the right counselor and let them help you guys get through this. You seem so close if not for this one issue. I understand it's a big issue but it seems like to only major thing keeping the two of you from completely reconciling.
I agree that she should remove OM from her FB. If she doens't call, text or email him then why not remove him from FB? How would that be any worse for this guy than her not communicating with him? I don't get that one.
Future, you guys seem so close. Don't give up now man. Good luck!
Yes, the A is the gigantic blue whale that sits between us. I am trying to show her a path back, but she still refuses to take it. She has this brutal emotional honesty, and she refuses to embrace our M while she knows she still has feelings for OM.
She is going back to see our MC, alone at first. We'll see what comes of that. Our MC isn't militantly pro-marriage, but she doesn't endorse what my W did, on the contrary, she was pretty harsh about it, but she knows what we here on the DB site know, fighting a wayward spouse only makes them run away faster. Now that my W is coming out of the fog, perhaps talking to our MC will help now.
There is a lot of good between my W and me. I'm not giving up yet, but as I said before, I may need to let her go again to see if she really wants to save our M.