It's too late to tell you this, I know, but a few drops of Frontline/Advantage on their neck once a month should prevent them getting any.

However, now that you have them... give each of your girls what the vet told you, and then get the vacuum cleaner out! I don't think you have carpets on, do you? Still, all the furniture have to be vacuumed thoroughly. You may even have to sprinkle some "flee powder" around the house - and in the vacuum clener too, ask your vet about that.

Good luck getting rid of them!