No, you didn't mention she was getting spayed and that changes everything. Yes, definitely get a biopsy done since she will be under anesthesia already.
Just remember that Dr. Center states that a diagnosis cannot be made from a biopsy alone. It must be combined with a Protein C test and/or imaging (preferably scintigraphy, not ultrasound).
Hepatic Vascular Disorders - WSAVA 2006 Congress