Ah, okay. Nothing here explains it, but this article at least taught me more about your type of chicken and is interesting.
Still, my only thought is that there's some vitamin deficiency going on with her. I hope she gets better!
What breed of chicken do you have? I ask only because with silkies, the first time any one of them starts acting weird, I break out the vitamins as it's no doubt a vitamin deficiency. I would get Poultry Cell, Nutra Drench, or something like that and put it in their water for few days just in...
Could she be molting? I have a silkie that just got over acting like that for several days. I gave them all vitamins (Poultry Cell) in their water but not sure it helped much. Regardless, it only lasted a few days.