It sounds like her grandma left one pot of money for all of the kids, because she said another relative also got his college paid for from that money not just her sister. They were dumbasses with the money, but if there is even a chance her parent's aren't completely worthless (there is), the advice to her should be to stay away from her parents for a couple weeks and make a level headed decision, because sueing her parents sounds great until you realize there's a good chance she won't get anything and her life may be worse for it.

If her level headed decision is to sue her parent's I'm all for it, but from the language of the post, she isn't making a level headed choice right now.