Fortunately, you don't need to do a serum test for Liver Shunt - in fact the Urine test is more reliable (and there is NO fasting!). I do hope it is negative, but at least you could rule it out for peace of mind. Go here:
http://www.canine-epilepsy.com/bileacids.html
You could def. try syringe water - or have you tried adding pedialyte or karo to her drinking water? Or add water to canned food? Did you try something carby - what about graham crackers?
My heart goes out to you - I so hope you get to the bottom of this.