Do you have a rooster?
When was her last egg?
What do you feed, including treats?
Have you checked her over for injury on the body and under her wings, her legs/feet/joints/bottom of feet look o.k. - no abrasions, scabs, bruising?
Could she have eaten something moldy, rotten, compost, toxic?
I'd work on hydration, electrolytes would be good if you have them. Once drinking, see if she will eat some wet mushy feed or bits of egg.
Photos of her poop?