Hi, Pilgrim!
I feel like you in that I have come on here in my struggles lately, but haven't been much support. Your post made me think of something I read recently about "the only thing we can do for others is work on ourselves." Or something like that.. that resonated with me. An anti-codependent sentiment, if you will.
It must be terribly hard to raise a teenager, and to see them hurt. I don't have one myself, but I teach them, and have close friends and cousins with similar situations to what you describe. From the troubled teen perspective (thinking of myself), I feel like what would have helped me is if my mom tried to work on herself and even would have pointed out where she felt she went wrong. I'm certainly not comparing you with my N-mom, you're clearly caring of your daughter and want to help, not hinder. I've always understood there were a lot of things passed down in my family, and I understood why my mom couldn't be there in the right way. But I felt, regardless even of her abuse and neglect, if I knew she loved me-if she could show me that- express her remorse or empathy for how she treated me, it would mean the world to me. We would be reconciled if she could do that. But she can't. It sounds like you love your daughter a great deal and may even overly-attribute some things to yourself.
My thought is only that if you express yourself to your daughter, show empathy, compassion, concern, and that you are working on yourself so you can be your best for you and for her, I think it would go a long way for her as well. You may already be doing that, and clearly want to. So, please be gentle on yourself. It's ok you've had your own struggles too, and things aren't perfect. Your kids want and need you around, caring for them, being supportive. This learning experience for her may end up helping her with future decisions. It's hard lessons many of us have made. Could she retake any of her classes? There must be a solution where she can still follow her dreams. I hope this isn't too much.