Of course you can bathe a kitten with fleas. If it is necessary, don’t worry about that. You will need to use an effective medicine or the vet may recommend another method of getting rid of them (such as injection).
You can also try combing your cat while bathing her and remove all the fur at the same time (please be careful though because not everyone has this skill yet). Bathing should be done once every week or two depending on how often you are able to get your kitty fixed. Cats aren’t like humans in that they do not sweat like us so baths must be more frequent if their skin gets too dry for comfort!