Ugh! I hope that whenever my bro, sis and I have to deal with this that we won't have those issues. I don't think we will and we hopefully have a longlong time- my parents are in their early 50s.
I feel for you guys. Like others said, there is nothing you can do, and your dad must have known what would happen, but it's still hard to watch her squander what he worked so hard for.