Hi. Sorry to here of this. Here are some links .... liver dx is basically treated the same regardless of the cause (generally)
Pathophysiology of Portosystemic Shunts www.livershunt.com both sites post a recipe for homemade diet...
Main issue: feed a reduced protein diet @18% hard boiled egg and cottage cheese are more easily digested proteins, along with proteins derived from plants as oppose to meats.
Medications should include Lactulose and Demamarin, and an antibiotic to start. The U of Tenn website explains these drugs in detail. She needs to be on these drugs asap. Call your vet.
Good Luck, and please keep us updated.