Hello Holly,
I would consider reading up on codependency like Pia Mellody’s books or go to a support group like Al Anon. It is hard to watch low functioning and hurting people get themselves into situations and for me it’s taken a lot of healthy boundaries to not get sucked into madness and unreasonability. I don’t think that there are any black and white answers from what you shared, but I hope you find those suggestions helpful.