At the start of my marriage break up (my ex. went off with someone she worked with) my mother-in-law actually suggested allowing her daughter to disappear with her fancy man and she would continue to care for my daughter/her grand daughter. That was shocking and showed the depth of ill will between them (some animosity existed between them over battles around the time of my ex/'s father's death, connected to the fact he probably "spoiled" her).
I think initially my ex. mother-in-law ensured I did get contact with my daughter, because she would not have supported my exclusion (and our courts were more firm then in support of NRPs).
Thanks for your post, there are many, many different aspects to all this, we may never resolve them all, but what a fillip it would be if we could resolve a few of them.
ATB, Graham