Again, I have to agree with Helen and Michelle.
Comb her over with a fine pitch comb (preferably metal if you have one) and drown the fleas in a tub of warm water that's got a squeeze of washing up liquid in it. Pay special attention to the back where it meets the tail, the armpits and the groin area. Then take her to the vets tomorrow to get some proper flea stuff - in a young kitten, a bad infestation of fleas can be dangerous if not fatal.
For a really young kitten I believe you'll need the Frontline spray as the spot-on doses are for kittens and cats above a certain weight. Either way, check with your vet. If she has fleas, likely she will also have worms because fleas are carriers of worm larvae, so get her wormed at the same time.
Cheap flea stuff for cats is a waste of money because it only repels fleas, it doesn't kill them - and as a result only pospones the problem for a while and will make it worse as the fleas will then breed...
A quick tip though. If you have fleas in the house, give all your soft furnishings a good vacuum. Pop a flea collar in your vacuum cleaner bag before you start and it'll take care of any that get sucked up while you clean.