Check her for eggbound. Search on here, on BYC "Eggbound". Also, it may be that she has parasites or worms. Have you checked her poop, checked her vent? Even if you don't see worms, she could have worms. Search here on BYC... "worming with Valbazen", "Worming"... "Eggbound", etc. Worms can cause limping and leg weakness. Also search Paralysis... that may be another problem. I read where some hens have been treated successfully with a lot of TLC.. being brought in, hand fed, etc. Sometimes they eat a slug or something they shouldn't and they can get past it with some TLC, scrambled eggs and yogurt, antibiotics, vitamin water, etc.
Warm massaging eggbound soaks... in the house. And, keep her warm, inside.
At six months it could be a laying problem, egg stuck, broken inside her, etc... poisoning inside from a broken egg inside her... Search these things here on BYC for more info.
Good luck.
