I really appreciate your feedback and concern everyone, it really helped.

Bonnie is (thankfully!) back to her old self. The vet felt she was probably just "under the weather" a bit because she checked out nicely for her exam. We had to coach her somewhat to get her back on track with eating her meals, but now she's joining the others with their little anticipatory dance as I prepare their bowls and eating normally again. She's spending her days her favorite ways once more: watching the birds, diving under bedcovers, and coming up to me for some love -- always on her terms, of course (my silly girl!). I'm so glad she's well! None of my kitties had ever gone off their food for three straight days, so this was a new experience for me!

Thanks again! It's nice to know I have a place to go for support and advice. Here's my girl, long and lean!