The vet discovered that her white cell count is very low, less than half of what it was a year ago. There's no real explanation at this point, except several I'd rather not think about. I had her tested for feline AIDS and feline leukemia when I first brought her inside, and she was negative. But she has a history of being out on the streets, consorting with a whole gang of other cats with sketchy pasts, so it's possible the test didn't tell the whole story.
Anyway, she's home now, with some different meds, and being doted on by me to the extreme. At first she was pretty miffed that I put her in the carrier and allowed all those scary strangers to touch her, but the trust rebuilding seems to be coming along nicely.
She could use your good thoughts, though, and so could I. Whatever the final diagnosis, she has a home with me forever. I'm just hoping "forever" isn't getting here sooner than expected. I'd much rather have a lot more "happily ever after."