I am not one of those folk who believe in the mantra 'famblee at all costs'.
I do think some contact is ok, but limited if a parent is evil or destructive.
The problem is, she is being destructive to the warehoused kiddies (why can't their own moo or duh stay home with them?) This might be difficult to prove.
One solution would be to report her to appropriate state agencies and let them sort it out. I would have no doubt this would end any relationship whatsoever, in which case you thank Whatever and be glad no more bitching and whining from her. Otherwise, only call once a week and when the 'horrors' start, simply state 'you will call back some other time when things calm down', and HANG UP before she gets a chance to vent spleen. If she starts in before you can, STILL HANG UP. If you have caller ID, use it. If you have call blocking USE IT.
You may simply be hoping for some relation where you could have a normal mother. Acceptance is the knowledge that she won't change, and the power is in your corner to do it. As such, drop her like a hot potato and quit trying to get her to be a real mother.
You WILL have greater peace of mind, and I think your husband would be happier as well. You suffer, he suffers, all suffer.
LIMIT YOUR CONTACT IF YOU CAN'T CUT HER OFF ENTIRELY.
Pardon me if I sound harsh. The reality that a parent (or parents) is/are bums is shattering. However, if the price of having a quiet, peaceful, fulfilling life is cutting off family, ANY family member, SO BE IT.
Peace is more valuable than famblee shit.