Is this the only kitten in the house? Why is it so young? Was it a stray?
If she has bad fleas, give her a bath, make sure to keep her warm, use a mild dish soap, dilute it in water, make sure you get all the fleas off of her. Dry her off reeally good. Also wash and treat any carpet, bedding, toys, etc that she was around because fleas are a pain in the a** to exterminate and you want your house to be free of fleas.
Flea collars don't work, if your house is free of fleas, you shouldn't need any flea protection unless a small break out occurs (fleas can come into the house on your clothes), and then you can apply a liquid or give her a bath. but hopefully that won't happen any time soon considering she is so young.