I don't worry about her having a good relationship with him. I think that's desirable and necessary. I'm not going to be one of those people that thinks "oh this relationship with AP will never last." AFAIK, OM will be her step father someday, and I intend to act as if that's the case with the thought that D needs to know that's OK and not have any undue stress over it. If this guy is going to be in her life, then D needs to not think badly of him. It [censored] (for me) but that's life.
D has a history of saying something and then saying "just kidding" if it's something that could be hurtful. When she says things like that she usually isn't "joking." Coupled with XW's change in attitude toward my parenting, the highlighting in court that I'm the "adoptive" parent while she is the "natural" parent, the fact that "someone" has brought up with D that I'm not "actually" her father, and our own history here (XW was telling D that I was her daddy within weeks of us starting to date). Add "I have a new daddy" and picture of OM holding D within six weeks of their meeting (and based on the pic, it's probably either that weekend, or the one after) and it adds up to a singular conclusion. Which is NOT ok.