Perhaps it's time to tell her how disappointed you are in her, that she would throw away your love and your marriage the way she did to chase a married man! And you don't know how you could recover from the way she has been lying to you and deliberately saying hurtful things to you. Perhaps it is for the best for her to move out. You are just not sure about anything having to do with her right now.
He don't need to move to fast or push or explain or anything. Let her sort herself out while he takes care of himself. Lay back off of her, but be there if she really needs it IE: hospital, or if she get sick. Outside of that I say he's having fun, and if she wants to join fine.
