You've GOT to get that dog to a different vet. Have you googled "veterinarians in Vidalia, Ga?" Try that. As for the teaching hospital in Auburn that needs a referral, have you called? If not, call and plead your case - cry if you have to (if that were my dog, it wouldn't take much for me to break down and cry on the phone, pleading for them to see her). Be desperate - cuz I think you are. Your dog's life may well depend on it.
Is there an emergency clinic near you? Perhaps they can refer you to a different vet, just an idea. What's the next largest city near you? Perhaps you can find a vet in a Savannah? Or Atlanta? (Sorry, my Ga geography isn't the best, I'm in Ca). It may be a very long drive, but it may well be worth it to spend a day. If you do find a vet that you think you may see, try to have a good phone conversation before making the trip, explain everything that's gone on, your frustration (and desperation), the lack of progress, etc and see if they think they can help you. Any good vet shoud be willing to spend a bit of time speaking with you on the phone before seeing you if you explain you'd be making a 3-4 hour trip - but be willling to pay for their phone time (they may or may not charge you). And, if you do end up going someplace, get a copy of Prissy's med records to take with you - it will save lots of questions and hassle if you can just hand them the stack of records (and with all her visits, I'm sure she has quite a stack). I just know if it were my dog, I'd be moving on to someplace else, and not stopping until I saw my dog turning around, and acting like she used to, wanting to eat, and enjoying her life. A dog with a constant blockage is not normal. A vet who doesn't seem to know what causes it, but doesn't seem to care to find out, either, troubles me.