A lot of BMs have irrational issues with the "new wife" of their ex... especially where children are involved.
All I can say is Please, don't take it to heart... life is far too short to worry about "her" (BM) tantrums. It is difficult for "her" to let go of the familiarity and so called life she once had with her ex (your dp/dh) and she knows she just has to get on with life but can't get past that hurdle. She will use any excuse to take her anger/embarrassment/inadequacy/shame/disappointment/sadness/grief - or whatever you want to call it, out on you.
Most of the time in many volitile cases, the BM uses the children as a weapon, turning them agains the new wife etc.
Most BMs cannot see their future without the life they once had, no matter how good their lives may be now, or how awful they felt before. She will eventually find her own road, or she won't. If she doesn't then all is lost for her, as one day, she will not have the children, she will be all alone. I hope that BMs who struggle to find their way do eventually find a path they are happy on. It is only themselves they are hurting in the end.
I don't think that any (most anyway) BMs want to go back to the way things were with their ex... I don't think that you have any concerns in that area... The BM will try to make some sort of relationship with the father, for the childrens sake, but don't forget, all they know of that kind of relationship is the marital one.
I suggest you hold tight, don't take any shit or rudeness from BM, but give her time to settle and see that her efforts to get to you do not work... and that she can have your attention, and that of your dh, when she is pleasant and cooperative. You are only human but choose not to be so personally involved with this upset. Not your problem... keep telling yourself that it is not your fault too.
The only relationship there should be is for the children. IF they see such hatred and upset then how are they going to turn out? Chill out and just let her get on with it.
Good luck... give it time.