You stated this well. And I completely agree. I never attempt to take over when it comes to my stepdaughter, but I am a concerned and active participant in her upbringing. I wouldn't be on this site if I wasn't.
"Perhaps if you could address this and work to make sure she knows she will always be MOM and you have no intention of filling that role..."
I'm not sure what BM's deal is. I don't know if she still has feelings for my husband and that's why she's so easily angered. I don't know if she's threatened by my role in her daughter's life... I'm not sure. And if it is me, and she's feeling insecure about my relationship with her daughter, is there much I can do about it? And I'm asking this genuinely, not in a smartass way. If you have any advice or ideas, I'm definately open.