What are you going to do in this confrontation? You going to say "him or me"? "I wont live in a 3 person marriage"? Then be prepared for her to say she doesnt love you and doesnt want to be with you and is ready for divorce.
What then?
I've reached the point where I can handle hearing this. If she wants to divorce me I will make it clear that I don't want that and I will leave the door open for her to change her mind as long as I can. She will have to do all the divorce work but I won't block her. I don't see the point of blocking her if she really wants out.