Plz help!!

So my cat has fleas. We dosed her two weeks ago with frontline but I believe it only got on her fur and then was licked off because I have combed eggs and adult fleas off of her today and every day since we dosed her. She is nursing a 2 day old kitten right now also. I want to re-dose her (and properly this time) but I’m not sure when it would be safe for her and the kitten. Please help, as I am extremely concerned for the kittens safety