What other ingredients are in the glucosamine supplement? I'll have to look when I get home and see if I still have the info on what I had Navarre on. The vet told me to look for a few other ingredients in the supplement. When I changed him to one of those the difference was very evident after a couple of weeks. Also it takes the glucosamine awhile to build up in the system, that's why at first the directions tell you to give a lot of pills at the beginning.
I know you've been very careful about how much protein etc she's taking in, and this might be a muscle issue, just being sore. Navarre used to get lame from time to time when he was growing, it would last a little while and then he would be fine. What has your vet said about how much to feed her? If she's not eating, I would watch that more than anything, but she may just being finicky, or if it's been un-Godly hot where you are, that may be why she's not eating too. She's a rescue right? Any idea on her past? I know she's young, and it might just take awhile for her body to catch up on any mal nourishment she endured before. I'll look for that info when I get home.