Hi....so, I am no vet, but a friend had some similar issues with her dog, and the dog had portosystemic shunt. This is a lucky guess, you need to listen to your vet or get a second vetenerian opinion.
But I agree with you, you have to be careful not to put her under some treatment that is uncomfortable to her, or more aggresive than the disease.
I hope you will come to the bottom of this, and If She is ok and functional, try some natural remedies too (it can’t hurt).
Sending you get well wishes