She talked about how afraid she is that if we do D that I'll tell the kids something like "it's because mommy doesn't love me anymore" and she'd find that devastating--which is confusing to me because for the moment, it's exactly true. Or that I might do something like fight for custody.
Because in spite of what she does or how she feels toward you and the M, she doesn't want her children to think she's bad.
My children were grown when I had an EA, but I will never forget the terror I felt at the possibility they would be told by my H what I had done. One of the most horrible things I've ever said to him, was when I told him I would hate him until the day I died if he ever told my kids. An "ultimatum" was all I had to throw at him. I was crazy enough to actually believe he loved me to the point of covering my actions and the truth from our kids.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!