We went to the vet yesterday afternoon. He took a culture (a lot of white cells and some debris--probably from the litterbox), took her temperature (normal), watched her walk (the limp was a bit more pronounced by the time we got there), and prescribed an antibiotic. Half a pill once a day for two weeks. He said the limp should go away pretty fast. If this doesn't work our next option is biopsy (taking into account Samson and Oreo's medical history). Gulp.
She spent most of yesterday afternoon snuggled up with me on the couch, purring and sleeping. So I'm forgiven for messing with her foot and than dragging her back to the place where she has to suffer all sorts of indignities from That Man in the White Coat.
I gave her the first dose last night, and already she's walking better. Huzzah!