Re: DD has a "secret mommy"
I totally agree. Encouraging her to keep things from you and implying that you would be upset with her about it is such crap. Their behavior is really setting her up to feel conflicted and that is not fair to her. She is 100% innocent in all of this and they are hurting her. I think you handled it with her very well and you are certainly going to need to address this with him. He sound like a bit of an idiot so he may not believe/understand your reason but the main issue is that they stop their nonsense.
Just in case.