I have a Maine Coon, she is 10 months old and frontlined by the vet religiously, last time it was two weeks ago, but today I found 4 fleas on her, how do I get rid of them if the frontline hasn't done its job?
As I understand it, the treatments don't kill the fleas, they just render them sterile so that they can't breed after one feed. I would get a spray to treat the house to make sure there are no eggs which will hatch and jump on the cat to feed. Get one from the vet, as these are formulated to penetrate the eggs and kill them, it is a false economy to buy a cheap brand.
I think the best thing is to comb the cat well and kill any live fleas you find by squashing them on a tissue with a fingernail. It is possible that Frontline isn't working, so consider switching to another type, we use Advantage.