What exactly can we do for people who don't want to do anything for themselves? That is the first problem to try and get around. Making her see that she has problems. At her age I don't think there is anything you can do legally. Unless you were to try and adopt your own grandkids. Stating that she was an unfit mother and her husband a drunk, abusive father. This might open her eyes at least. No doubt she has turned her back on your love. But you love her and your grandkids too and I would do what I thought best for them. You daughter mightn't want this. But at times we have to be cruel to be kind. I would challenge her as a mother. In a court of law. Show her that you are not giving up on the kids. Once you have your day in court you can say things and she will have to listen. About her problems. About your love for her. Wanting to help her out. Seriously I can't see any other direction you can take it and make an impact. Because she is old enough to do as she wants. That seems to be what she is doing. Probably not the answer you expected to read on this forum. Not medical in any sort of way. Just a common sense approach.
My humble advice would be to hire a lawyer and let him/her take on this horrible burden for you legally. MrGreen wisely pointed out that at her age, you have no say in her life and obviously no control...........she has been through some rough times, but her personality change is rather frightening. My one and only concern at this point would be for the grandkids. I agree with MrGreen that you should go after custody of them until your daughter gets her act together. I think you have a very excellent chance of winning custody, as both she and her ex sound like totally unfit parents. Enough lives have been ruined here already, let's worry about those kids first. Maybe once your daughter realizes what she has lost, it may bring her around. I am so sorry you are having this problem in your life. It must be very difficult and sad, such a helpless feeling. I really think getting the kids away from possible physical harm and without a doubt, emotional abuse, should be your first priority. They need love and caring and stability to begin to undo what has already been done to them.
Again as MrGreen said, sometimes we must be cruel to be kind. It's a sad truth.
Please let us know how things are going, OK? Post as often as you need. We will always be here to listen.
Peace
Greenlydia