Originally Posted by afar
I feel like she is the wall that he stops at to unload all of his happiness and love and then comes home to me bitter and hostile. What can I do?
I have a guess as to why you might find him bitter when he comes home.
He has feelings for this girl and doesn't have the courage to say what he feels or what he wants. Between you and the marriage counselor it is unlikely there were many options for him but to capitulate about "closing" the relationship. While you probably already know that he has romantic feelings for her, it's very likely that what he isn't telling you is that your disapproval is not reason enough to shut it down entirely. Further, it seems very likely that he resents you for it.
He digs her for all of the reasons he was into you when you two met. Only now, she's offering him his "freedom" and you are offering him the opportunity to "sacrifice". I'm sure, given the right circumstances, he is still very much into you but currently it sounds like there is a conflict of interests going on.
I'm not casting judgment on your situation, just giving another perspective on what might be going on.