Just bumping this up, but any idea why? Has she sustained some sort of injury, did she have problems as a chick, ie how long has this been going on? Was it gradual or sudden? Could be a vitamin deficiency; you might try Aviacharge; chickens seem to have a lot of neurological issues stemming from different things. We had a pullet about that age with a similar problem; it was progressive and we were not able to do much for her although we tried a variety of things, including the vet in the end. I guess if she were mine I would give her the Aviacharge just to give her some extra help in dealing with whatever the problem is. Also, check her feet/ legs. Might be a sprain or injury. We had another pullet who was limping, no visible sign of injury, no swelling, nothing. We confined her to a cage, where she could see the others but could not run around much, no flying/landing, no perching. Gave her vitamins and best feed; she was confined for about eight weeks, and made a full recovery. Probably would not be a bad idea to keep her confined and at least semi-isolated from the others for a bit, til you can get a better grasp on the problem. Good luck.