Oh dear!
Have you tried a vitamin supplement or something like the rickets diet in case it's dietary?
If you fill in the sticky questions and post the answers in your thread you'd probably get a wider set of answers.
Is she young, could it be coccidiosis?
I'm sorry I have no other suggestions, but if it was happening here I would probably isolate her in a small cage, make sure she can eat properly, check her body weight etc, give a mixture of oatmeal/yoghurt/mince/grated carrot or whatnot, and check her droppings.
regards
Erica