In this situation, I tend to agree with job, leave it be and don't respond no matter how much you want to scream at her. She deserves it! But, she is taking her brother's side and no matter what she may see now or later, she will never care to see your side. Some people are blindly loyal, I have seen it first hand. My uncle (pretty sure MLC, chucked his family for another one) and his sister (my aunt) could not talk enough trash about his now ex-wife. Even then, I couldn't stand it and there will be family members who hate what he has done and will not attack you. But there are those who will refuse to see.
If you are able to block her, do so. If she should contact you again, I would simply reply "I would appreciate if you would please not contact me again."
I know it hurts like the devil, WR. But you take care of business. And so what if he is homeless, etc? Whose fault is that? You weren't given a choice when he unilaterally left your M, but you have lots of choices on how to go forward and protect the rest of your family. And as you said, after 20 years, he should have known. Of course, he should have known that fantasyland did not exist, but that is a whole other topic....
Hideous woman. Betcha she's got some issues of her own.
