Don't apologize to W for D15's feelings toward her. D15 needed to get things off her chest and it's strictly between them. It's best that you stay away from them and allow them to figure out their relationship on their own. Frankly, I'm glad that your W is receiving some real raw insights on the pain and destruction she's caused to the whole family....not just you.
If and when W comments that she's not sorry about the OM, I would tell it straight to her that it is a very selfish thing to say and not accepting the responsibility for this horrible choice. I really do think this needs to be said to her face. You cannot afford to pussy foot around this issue.
What do really have to lose here? Other than your balls??
