Thanks for the additional info, that's very helpful.
Something just isn't adding up for me on the description here. Her liver enzymes shouldn't be normal if she's icteric (jaundiced). Icterus can be caused by pri***** *****ver disease (sclerosis, portosystemic shunting, drug reactions, infections), but this should have showed on a biopsy. It can also be caused by hemolysis, which is destruction of red blood cells, but this would have caused a severe anemia on blood work. It is possible that her liver biopsy could be normal if she's got a bile duct obstruction - which is usually but not always detectable on ultrasound examination by an experienced vet or tech. but again, with a bile duct obstruction I would expect more than just her WBC ct to be a little high. Bile duct obstructions can be caused by masses (tumors/cancer) or by inflammation associated with pancreatitis, which, again, would likely be detectable on ultrasound or through blood work. I've also seen icterus with gall bladder abnormalities like stones and mucocoeles - these are fairly easy to diagnose with an ultrasound. Mucocoeles do require surgery to correct, stones may require surgery or sometimes are treated medically.
If she's not already in the care of a specialist like an internal medicine specialist, this would probably be your next step - to get a second opinion from a specialty hospital. If he's already in the care of a specialist, I would stay the course with the recommendations made by your specialist. This is a complicated problem and I'm not going to be able to get a full picture of what's going on here third hand like this - there are too many variables, unfortunately.
I will say, though, that it's reasonable to cover with antibiotics for an icteric dog as well as support with milk thistle or better yet sAME - a product called Denamarin has both- this is what I use for my liver patients. It's also important to continue symptomatic and supportive care by treating individual symptoms like nausea, diarrhea, dehydration, etc as they come up. Unfortunately when I have older pets who have mystery illnesses that the diagnostics aren't sorting out, I start to worry that there's something cancerous process going on. There's no one specific test for cancer, so until the pet is improving or we find an answer, I usually keep hunting.
Please let me know what other questions I can answer for you :)