Omigosh, RT! I am glad your mom and friend spoke some sense into your head. Oh, and turn that word, 'coddling', into 'loving'. As I was reading your post, I was thinking, "the woman is nuts ... how dare she say her daughter has no power (way to go to make your kid feel helpless) ... why does she not take her dress shopping to start in a small way to get the bond between them back on the road?" It almost sounds like your W is back in her teens (where it's all about her), and is upset with your daughter, because she perceives her as betraying her, but she is the one that left, and betrayed your daughter, and you, and your son. But, she is in MLC mode and won't see that now.
I am sure there was a time when your W was a great mom, and a wonderful W, but it seems she is in Never Never Land at the moment, if her interactions with you and your daughter is any indication.
Anyway, not sure what advice I can give you because you are doing all the right things. Good idea to talk to your C about what to do about your D. I would never force my daughter to talk to me in counselling ... firstly, it is overbearing, and secondly, you're unlikely to get anything out of a forced situation, so no point. She'll just end up resenting her mother even more (and I don't regard myself as a particularly brilliant mom, but I even can figure this one out).
Maybe your mom could take your D shopping for a grad dress? Of a favoured aunt?
Take care.
Me:57 H:52 M:28 Got another lawyer last year and filed. D35,S/D twins28,D22 EA4/04 End? Who knows? "Life is like a mirror. Smile at it and it smiles back at you." — Peace Pilgrim