Revolution won't keep the fleas from getting on her but it will kill the fleas within a few hours after they get on her.
Your adult cat probably has a pretty bad infestation and should be treated. If she does not tolerate Revolution, then you can try Advantage or Frontline Plus. If neither of these is acceptable then you can give her Capstar, which is a pill that kills adult fleas. You have to give Capstar every day since it does not last in the cat's system but it is safe to do this and to use Capstar along with other flea products.