Do you know what the bile acids test number was? That would tell you if you may be dealing with a shunt or perhaps just asymptomatic mvd.
Before you panic, retest her. Then if her BAT is still high, a protein C test should be done to see if a shunt is likely.
Here are some good links to information from two experts on liver disease, Dr. Center and Dr. Tobias.
Hepatic Vascular Disorders - WSAVA 2006 Congress The University of Tennessee - College of Veterinary Medicine - Portosystemic Shunts