I would make sure that she is getting fed and watered a few times a day. I had a hen once who lost her balance and could not stay upright for about 5 weeks. Eventually though, after feeding her mushy wet food, egg, tuna, and cat food, she was back to normal. Human B complex 1/2 tablet daily can...
If you’re not feeding a balanced layer or all flock feed as the most of her diet, then it could be a vitamin or mineral deficiency. Mareks or an injury would be suspected as well. Chickens should not receive corn or scratch, except as an occasional treat. A balanced feed such as the egg layer...