(((Baxter))) - I'm sorry you're going through this. FWIW, I'm a recovering addict, as well as a recovering codie, and when I was using (crack), it was ALL about me. I actually distanced myself from my family, but we are very good about putting blame on someone else because we don't want to deal with our own issues.
I can tell you that justifying yourself isn't going to do any good with her. I also understand you want to maintain contact for the grandkids, but maybe saying something like "I'm sorry you feel that way" and changing the conversation would work? I'm sure others will be along with better suggestions. I've had to go a day or two with no contact with my dysfunctional family, and I LIVE with them.
Hugs and prayers,
Amy