You'll always be her dad, of course, but she is a grown woman, with all of the rights and responsibilities thereof. Your daughter is not even "on the edge" of adulthood. She is a full adult and has been for some time.
You are making a choice here, and it is yours to make, End. You are choosing to continue to parent your adult daughter. And thus, you are choosing to take on all of her "stuff" at the same time. That is what we are saying here.
It's time to stop parenting. For most of us, way, way, way past time. Is it hard? Yes. Do our feelings say differently? Yes.
But End, we have learned that feelings are not facts. That is a key premise of Al-Anon and one it took me a long, long time to grasp. I thought if you felt it, it must be true.
Not so. You can feel sad and upset and anxious about your daughter, and you can choose to not react to those feelings. That takes practice and work, to stop, but it is possible.
I used to lie awake at night and think about this. For hours. "If he has a mental illness, then is he still responsible for his behavior? If not, then I must be involved, as his mother, right?" On and on and on, I would obsess over this.
My son is not psychotic and thus knows reality. If he were psychotic, perhaps my answer would be different: I would need to be involved.
But he is not, and yes he has depression and anxiety, but he is still responsible for his behavior.
All mental health professionals will tell you that straight up; that's not my response, but it is theirs.
I know this is hard stuff to hear and to grasp, but it is healthy thinking and healthy behavior, I believe, and so very different from what our yearning hearts want us to do.
That is why we have to work for this new way of living. And it's worth it.
As always, take what you like, and leave the rest. Warm hugs.