you are definitely not a bad parent. Just g-d damn tired! I relate. Drama after drama and we just keep on coming to the rescue and then are met with anger, manipulation...etc..I just went through dramas with my 22 yo daughter who has had anxiety and depression issues since she was 16. I have always come to the rescue no matter what whenever she has needed me. Now I seem to be the one she lashes out at. When she is in a crisis mode she comes running to mom for comfort ,help,whatever. then when she regains herself , I'm in her business, controlling etc.
I know i need to start to detach, hard as it may be to do but i need my sanity back and she needs to learn to be an adult. I try to tell her she needs counseling again (she used to go and i feel it helped) but she is 22 and i can't make her. So all i can do is pull back and let her make her choices. I feel the emotional drain as you do too. Take time for yourself