So many children were affected so negatively by Covid and lockdown.
My dd (not my ND child), was admitted to a psychiatric hospital at the end of 2020. She had already had a diagnosis of PTSD and major depression, but the lockdown just exacerbated everything, and she just could not cope. She tried to run out in front of a car, and was then admitted to the psychiatric unit immediately. The thing is, that I did not even pick up on just how bad things were, until this happened.
There are a lot of factors that may be coming into play for your dd. And perhaps everything in just now becoming unmanageable for her.
I know you said she is hesitant to therapy. So was my dd. But I stepped in and overrode her decision, because she was not in a position to make a proper decision for herself. No I wasn't popular, she hated me for it (for a while). I was not allowed to visit and she got a phone for 15 minutes a day. She cried for me to fetch her for 15 minutes every day in the first week. I didn't. It nearly took me out honestly, it was one of the worst times in my life.
But she needed to be there as she needed the help I could not give her.
I think you need to do whatever you can to get your dd to therapy. You are her parent, and it is your responsibility to do what is best for her. No matter how hard it is.
I will just add in, that my dd is flourishing now. She lives in another country, she decided to get out and travel and see a bit of the world. Has met the most incredible people in doing that and is enjoying her life so much. She is 23 now, so also still a young adult. I never would have imaged this is where she would be 5 years ago.
It is hard. And @bendmeoverbackwards it really is okay to step back and say you need help to help her. You cannot keep doing this alone.