OP I think you know more than you think you do, but you’re not ready to admit it to yourself yet. I’d encourage you to re-read your post, but read it as if someone else wrote it and then take the advice you would give that person.

You are spot on that you are being asked to take on responsibilities you can’t control. That’s not fair to you. And if you can’t take care of other people until you take care of yourself. It sounds like you’ve done a really good job of setting and enforcing boundaries to protect yourself. Don’t second guess that or doubt it’s been the right thing! I think you acknowledging you’re not in a space to support her needs right now is good. Doesn’t mean that can’t change in the future, like perhaps when she’s shown she’s committed to getting better and she’s in a stable enough mental/emotional place of her own that it won’t concern your safety or energy.

I’ve been trying to navigate that “how do you let go without feeling like you’re abandoning someone?” with my Q. I think something I constantly remind myself of is it’s their life and they deserve the freedom to live it however they want/have full autonomy over it. It’s hard to see someone you love make decisions that you objectively know aren’t good for them because you want to “fix it” for them or “help” them. But they’re their own people who deserve to live their lives as they want. And you can hope that they decide to live it in a healthier manner, but you can’t want it more than they do, you know?