I am a moderately-high-conflict stepmom on the other side of this story. Through my lens, when BM talks about SD feeling ‘rejected’ or ‘forgotten’ it sounds like projection - combined with BM’s backstory it makes it really hard to hear it any other way. When BM gets more insistent, I get less likely to listen.

When BM says her daughter is ‘pretending’ to be happy at our house but then is her ‘true self’ at mom’s, I immediately ask why SD couldn’t possibly be her true self with us and just telling her mom what she wants to hear.

I’m not saying you’re doing anything wrong. I’m just being vulnerable to an internet stranger because BM is sure as hell never going to hear that stuff.

If your daughter is truly struggling and you don’t think it’s projection and you don’t think she’s just saying what (she thinks) you want hear, and your ex and his partner aren’t being proactive, my best advice would be to get her in therapy. Therapists are amazing at getting to the root of these dynamics and will give helpful advice to both households. Having a third party involved really makes it all less personal.