This sounds wonderful KnittenKitten!
As I think I mentioned before, other creatures can get depressed. Cats brains have been studied as models of human neurology because of their similarity, and both cats as well as dogs have been treated successfully with SSRIs, for anxiety and depression. (Not suggesting you should treat Ezri, but i do think her illbeing could be a mood thing, either seasonal, or related to a recent stress factor that might not be obvious to.)
As a tortoiseshell, Ezri is getting on in years. I don't know if, like humans, cats produce less melatonin as they age due to pineal atrophy (vet will know).
If that were the case, it could explain a seasonal depression as of this year, but not in previous years. Also a tentative treatment could be tried - adding sources of full-spectrum (white) light around the house. Alternatively her vet could prescribe a feline dose of melatonin for wintertime. Neither would hurt her - at worst, there would be no effect.
Anyway i'm glad Ezri was active, sociable, and hungry yesterday!
Hope it keeps up!
~ waves ~