D...I realize there is no OM in the picture, according to W.
Why did she decide D was the only option? I can't quite recall. I don't think Sandi went into a full-blown affair back when she was wayward, either. The thinking was very similar, though. I believe that's what she's trying to get through to you. Your wife is wayward, OM or not. I don't think your approach would change.
She fired you as H. You don't want to be friends. She's cake-eating. You allow it.