Yikes, that does sound like pretty bad hip dysplasia to me. Did you "catch" her on the rump? A friend of mine had a severely arthritic/dysplastic dog and all of the things you just mentioned would aggravate his condition to no end. It's no wonder she yelped

If the vet could actually *feel* her loose hips, I would suggest getting x-rays done and sending it off to an expert to diagnose your options. HD is a slippery disease and can actually be dealt with quite simply.