I think that if your normal vet has very little experience with LS and bile acid testing then the best bet would be to go to a university. They are way more educated on this topic. I was telling my first vet what tests should be done, redone, next plan of action. It shouldn't have to be like that. I would make her an appt and even if it is a bit of a drive they will be able to guide you through the rest of the testing, a bile acid test doesn't rx a livershunt. It is just a good indicator. There will be more tests if her bile acids are elevated. It would be nice if you were working with a vet who knows what to do next. You should also join the yahoo group
Liver_Shunt_And_MVD_Support : Liver Shunt & MVD/HMD Support
They are all really knowledgable and helpful, there is also alot of info to read through that will answer most of your questions.
This is all such a scary process, I hope that you are able to get answers soon.