Well, Maggie just vomited and then hesitated before slowly eating her dinner. I called the vet and we put her back on the daily dose of prednisone (we had dropped it to every-other-day) and if she seems ill in the morning I'll take her in as an emergency case. Since she has an iffy liver I'll not be taking any chances.
The symptoms last time (when her liver failed completely) was a total lack of appetite - she actually backed away from food. She DID eat tonight, but without much enthusiasm. Usually she eats like she's starving. We'll see how she does with her breakfast.