Princess is doing a lot better. Before she went to the vet, her fur was thin and she had flea bites all over her neck. After she had some medicine, her fur got back to its usual fluffy state and the flea bites (at least mostly) disappeared. We just sprayed both cats with flea spray recently, and had the house flea-poisoned, so that should get rid of the fleas. If it doesn't we will try flea collars, probably. Princess was pretty good about taking her medicine, but when we were flea-spraying her, she wiggled around and tried to run away.