I can see it, though. Dad admitted he made a mistake and apologized to her. He sought forgiveness, and she granted it.

Mom not only never admitted her mistake, she is accusing her daughter of making a mistake in not just getting over it, when it took counseling for her to get over it. Sorry, but telling your pre-teen daughter that her father is cheating is a pretty crappy thing to do and ranks on the "Don't do this" list for a parent.

I agree that the LW needs counseling. But Mom's earned the lack of forgiveness, just as Dad earned being forgiven. It's to bad they didn't get her help back when it really could have made difference.