re: Complicated situation. Advice appreciated. Will try to be brief.

Whatever you do, make sure things are done on your terms. As you've said she's a bad decision train wreck, doing things on her terms will not end up well for anyone. If she doesn't want to do things on your terms then she wasn't ready to accept help from you anyway. It may be sad if you have to turn her way, but you getting dragged down into her drama won't help her and it will hurt you.