Could you have your own vet of choice examine her?
We had a TB filly that flipped over and broke her tail as a yearling. She was really sore and couldn’t move the tail at all, and one vet told us she was basically done. We called a great vet who does chiro and acupuncture; she examined the filly and did an acupuncture treatment, then gave us a special light and showed us the acupuncture points; we held the light on those spots several times a day and the filly began to regain tail function after a couple of weeks. Her tail was never 100% normal but she was able to train and win a few races.