Has she been checked for hyperthyroidism? I honestly wouldn’t try a liver aspirate without ultrasound to guide me to a diseased looking area of the liver. My personal experience with veterinary colleges is that they are less expensive than private practice. It may seem more expensive because...
Have you tried ondansetron for nausea/vomiting? Or mirtazapine as an appetite stimulant if that is needed. It can be made into a transdermal ointment. An ultrasound guided biopsy is really the best route to a diagnosis at this point.
Have you had bloodwork done? It sounds like your cat would benefit from a liver ultrasound and ultrasound guided liver biopsy. You probably need to see a specialist or go to a school of veterinary medicine. The second option would be more economical.