Dorothy16 your attitude toward your children and the way you talk about a bad situation just oozes unconditional love. Even strangers on the Internet can tell that you probably didn't do something to deserve being CO - or rather, if you did, that you are reasonable enough that a good open, honest discussion could mend what's been broken. Whatever happened between you and your daughter, I hope you get that chance.
Smileless, I can see how much your son's behaviour has hurt you. I am not in any way saying that you're wrong about your DIL. You are in the best position to know the truth, not us. I'd just like to point out to you that if my MIL came on here, she would probably tell a very similar story to yours. You really can't expect strangers on the Internet to know, from one side, or even after hearing both sides, whether what's really happening between a mother and her son is the result of a mother who is incapable of seeing how her behaviour is abusive, or a new partner who is abusive and attempting to isolate the partner. In any given story, those are two equally likely possibilities.
I'd love to say that, in our situation, people will understand that I'm not abusing or controlling my husband by insisting that his mother is a danger to our son, because we are open to her having a relationship IFF she changes her behaviour so that it is no longer abusive. Unfortunately, we know from experience with my SIL, who didn't actually cut her mother out but just didn't fall for the emotional blackmail when her mother threatened to cut herself out, that that story was told by my MIL as her daughter cutting her out for no good reason. So wherever my MIL tells her story, it's likely we might sound like the bad guys. We have to get past our desire for others to like us or agree with us and do what is best for our son.
When the situation is turned the other way round and it's an abusive or toxic partner, it's even harder for the party who is in the right to appear that way, because their choice in the situation, if they are given one at all, is to allow the partner to abuse the child and themselves, without question, or to allow the child to cut them out. The grandchildren are collateral damage in that breakdown, not at the centre of the issue. It is so much easier when you can simply look from the grandchild's perspective and then choose to act in their best interest.
What people do when they question whether you were actually part of the problem is technically victim blaming, and that is wrong. Unfortunately, when you're dealing with abuse situations, one of the most common tactics abusers use is DARVO - deny, attack, reverse victim and offender - and that sometimes makes it really difficult for outsiders to identify who the victim actually is, sometimes even for the victim to recognize that they ARE a victim. That doesn't justify or excuse victim-blaming, it just makes everything really convoluted - which is why an Internet forum is inherently going to be a place where it will be difficult to get people to say, without doubt, that a particular party truly is the victim (especially so if the participants in a thread have been the victim and had their abuser DARVO them). It is equally possible that neighbours and friends sympathizing with you could be proof that you are the victim, or proof that you are an abuser who is very good at DARVO. It's never going to be possible for strangers on the Internet to tell the difference. I don't say that for your situation specifically, because it's for any and every abuse situation, and that is why the argument just won't die. If you believe you and your son are victims of an abusive DIL (and I'm not saying you aren't) you will find more support in in-person support groups, where everyone there is in the same (or at least a similar) situation - because you deserve to be supported and not questioned.
What everyone can agree on, is that even in situations where the CO is justified, the separation hurts on all sides. Everyone misses out on relationships, and everyone will need to grieve those losses. Sometimes, that's what needs to happen because that is what is healthiest for all involved; sometimes it isn't, but either way, it's a lose-lose situation.