You have been doing a wonderful job caring for Brandi, taking her to the vet repeatedly and now syringe feeding her. As you know, cats are notorious (being prey animals as well as predators) for hiding their symptoms until they are really sick. It can be a nightmare for both vet and caregiver to figure out how to help them, especially when test results don't give you the answer.

I have fostered several cats who either barely ate or stopped eating because they became depressed after being taken to the shelter. Some have taken months to get back on their feet. Your vet will have checked her liver enzymes and would have said if she had a liver infection or fatty liver disorder, both of which cause inappetence. Even without such a definitive result, she may be feeling slighly nauseated because she is eating so little. Have you thought of trying Cerenia (an excellent anti-nausea medication which can be given by injection or daily pills for 4 days, rest, then 4 days more)? How about Mirtazapine (an appetite stimulant with slight anti-nausea properties)? In your shoes, I would be doing what you are doing, force feeding her. I've kick-started (sounds awful, but I don't mean a physical kick) several cats into eating properly again by force feeding them for days and even weeks.

Please keep us posted, and good luck on bringing Brandi back to her usual self.