It sounds like some sort of head injury. You have a hard decision to make. In my experience, she might recover, but it's going to take time. Weeks. The other choice is to cull. It certainly won't hurt to try the B-complex and vitamin E that @azygous suggested.I kept it indoors for a day and it doesn’t seem to be much change. Ill try to stop by the store and get some vitamins see if that helps.
But again, even now it looks lively and healthy. Just not able to prop itself on its feet. Still poops normal poop. Lays normal eggs. She moves around alot back and forth from the feed and water.
I had a bird that I found like that. I actually did spend weeks working with her, and she would start to recover, then get worse again. After about six weeks, I finally chose to cull.