JacobJoel - Thanks for your perspective on being a SM. I am also one as my husband has custody of his 2 children. My daughters situation is very different however. My 12 year old son absolutely adores his SM. I think she is a good person and she has done good things for my ex's relationship with my son.
I would absolutely not at all recommend you go to court to try to change anything. Your kids have a certain relationship with their dad and people he brings into their life and there's a wide spectrum of what's acceptable. I'm sure neither parent wants to try to dictate that for the other.
Your daughter and stepmom have their own relationship separate from any other child and her and it just is what it is. You don't have the whole story and never will. I would think a first step would be to talk respectfully to her father about what she's told you and say you'll leave it in his hands, maybe daughter would like to go to counseling with him sorta thing and then stay out of it.
Too often in these situations, CPs allow the child to do "splitting" which children do throughout their lives naturally, but it gets exascerbated in these situations where children can turn their back on the parent (or stepparent or extended family) that they feel like and shut them out. Not only is this bad for the parent-child relationship for the obvious reason, but I would be concerned about the future ramifications for that child to hang in there and work through their own relationship issues in the future with their own spouse, kids, and friends.
