Oops--I just saw this comment.

Nima isn't due for her shots until next March, so she lucked out. It'll be a lot easier to just deal with one cat then.

I think cats sometimes sense that something's going on. A cat of mine (who died last year) heard me talking to the vet about bringing him in for a blood test, and the cat (Chaos) hid while I was still on the phone. I never figured out how he understood what was going on.