You know, I think I would just quit worrying about it. "She's stil her normal self." I would just let her live it out, without a lot of other changes. Chickens hate change. The end will come no matter what, death is a fact of life. Just let her be herself.
I think she is getting old, and the end might be near. She sounds like a bit of arthritis is setting in, and probably aggravated by the weather.
I would not stress her out, nor would I take her to a vet. I might bring her inside, to get her thoroughly dried out, but change is hard on chickens...