Did she have a Protein C test? That will tell you if she has a shunt or not. Although usually BAT results are over 100 if there is a shunt, since she has seizures it could be small shunts.
Here is information on the Protein C test:
Comparative Coagulation -- NYS Animal Health Diagnostic Center
I would really urge you to take her to LSU. Most vets just don't see enough cases of liver shunts in their practice to know how to diagnose them. You can waste a lot of time and money dealing with a local vet.
I am very concerned about a dog with possible liver disease being on phenobarbital, too.