She can use frontline spray on them, it is safe for kittens from 2 days old. What I do when they are young is spray it on a piece of damp cotton wool and then wipe the kittens with the cotton wool, it prevents over-spraying them and they are then not afraid of the spray either.
1st vaccinations are normally at 9 weeks.
If they have fleas they will also need to be wormed and she will probably have to have them vet checked before any decent wormer will be prescribed. Probably best to get them checked over anyway to make sure they are not anaemic(sp) from the fleas, and to get their age checked. If she has been told they are six weeks old, they could be younger!!
Wish her luck with her new charges.