Thanks for your advice BT. We've always had cats, so I'd be surprised if our house was free of fleas. But we have 2 cats - brother and sister from the same litter. Brother is OK and we managed to get him to the vet. But his sister would rather starve than come into the house at the moment. I'll try the cat treats but I think her suspicion will outweigh her appetite.
I really need a cat charmer!