Hi, I'm so sorry to hear about your Pixie. I know this must be so difficult for you but it's clear that you care so much for her and you are very determined to do all that you can for her. She is really blessed to have you.
I hope your vet visit tomorrow will clear things up some more and provide you with much needed answers. It sound like you have a strong sense that she is suffering from Hepatic Lipidosis and if it does turn out to be the case there is link I found that I put below about a woman who had 3 cats who had this condition and though their prognosis was very grave, she was determined too and they are all doing very well today. On the site she writes about some of the many different approaches she took to treating her cats (everything from warm compresses over the liver with dandelion flower essence to sub-q fluids and daily supplements). She mentions that she fed them canned A/D by syringe multiple times throughout the day. She believes the condition is reversable and her site might be helpful for you. Maybe you could run some of her suggestions by your vet and see if they think he/she thinks it would be safe for Pixie in addition to whatever they are prescribing for treatment.
Link about Feline Hepatic Lipidosis

I also found a book online of natural remedies written by Martin Zucker and there is a mention by one of it's readers about how it helped their cat with fatty liver syndrome. It might be worth a read and any possibilites for natural treatments could be discussed with your vet to make sure that they're safe for Pixie.

This is the quote from the woman:
"Finding this book was a Godsend. After purchasing several other "natural cat care" books, this book exceeded all expectations and made the others a waste of money. This is the only book you'll ever need to keep your cat healthy, or in my case...to save its life. After my cat was diagnosed with a life-threatening disease called Fatty Liver Syndrome, I followed the suggestions of several veterinarians in this book, as well as utilizing "conventional" medicine with my local veterinarian and her blood enzyme levels were normal after only 3 weeks! Normally, recovery takes twice as long."
You mentioned that she isn't that keen on eating but is she drinking enough water? If she is dehydrated it could really make her listless as well. Your vet will certainly be able to tell you if she is dehydrated tomorrow and if so, maybe he/she might be willing to send you home with sub-q fluids to administer to your cat yourself. I used to give my 20 year old cat who had kidney failure 100cc's a week for a few years. It always amazed me how much energy she had shortly after getting her fluids. Of course, her disease was entirely different than what Pixie is facing but being hydrated is important and might help her get on her feet and get stronger. Might be worth asking the vet about.
I really hope Pixie will make it through this and that the two of you will have a wonderful long life together. You both certainly deserve it. Hang in there!