One thing you could do for her yourself is massage. I've seen what a huge difference it makes for my crochety old lady, Star. Star LOVES it, and afterwards she's more relaxed, and less stiff. The effects seem to start to fade after a day or so.

Wilbur too has always had a limp. X-rays revealed what looks like an old injury from a car. A Glucosamine supplement each morning helps him, but doesn't totally eliminate the limp. Massage has helped with him too.