Poor little girly girl!!
I hate to sound barbaric
, but have you considered glucosamine in the form of an injection, such as Adequan? I am by no means a dog expert but am extremely educated in equine nutrition and lameness and know that the IM Adequan injections are much more effective in horses than the feed through variety, which in horses has not been scientifically found to be beneficial.
Anyway, it's just a thought (and I know horses are so different from dogs but anyhow). Sorry if it offends you!!
On a second note, have you tried probiotics for her little tummy?