Yep, break the flea life cycle. Easy to say...
The pills that you are giving Mom contain, or maybe are only a growth regulator. This means it retards or stops the development of the flea eggs from the fleas currently on the cats, which effectively ends the cycle, sort of. The fleas still in the house and ones in the cat's environment that haven't hatched yet have to be dealt with. Be especially vigilant in keeping the kittens as flea free as possible. Fleas have been irritating Man for...ever? So you just know they aren't going to be really easy to get rid of. Following is a website on flea control...
Http://www.marvistavet.com/html/the_flea_control_center.html The section on flea biology will give
An idea of where the fleas in the home are likely to be found, and the part about the various control products may not be appropriate for a mother and kittens. Too many fleas on a kitten can kill it from the blood it loses to the flea bites. Yes!
Am going to suggest a non-chemical treatment that, if applied as directed and carefully, should kill fleas wherever they are.
DE, or diatomaceous earth, (Google: DE ) is a natural product available from mining in ancient seabeds. It is the skeletal remains of ancient algae called diatoms that have died and fallen to the floor of the sea, where they have piled up into a layer deep enough to be commercially mined, and inexpensive. You need to get the 'food grade' type, which is made from fresh water diatoms. There is a more common type used in filters for swimming pools and scores of other uses, which you don't want. Here is a site describing it, and offering to sell you some (which you probably don't need to do). You don't need the book, but see what they have in that section anyway.
Try garden supply, animal feed stores, maybe a pharmacy? At least they may have knowledge of just where to go. Mention D E. Anyone familiar with it will know what you mean, and you won't have to remember diatam.......whatever. One or two lbs should do it for the cats, more if you use it in the house, etc. If you use it in the carpets, leave it there. Vacuuming won't remove much of it once it works clear down in the fibers. (where the flea eggs and larvae are).
It is VERY fine, like talcum powder, and dusty if you get too enthusiastic with it. It is basically, a mineral crystal which has sharp enough edges to literally cut into the outer skeleton of fleas and many other pests as they move, once it gets on them, allowing them to dry out and die in a matter of a day or two. It can be safely swallowed, but inhaling it can be bad for the lungs if you, or a cat gets too much. If you pour it on the fur and gently 'wipe' or brush it into the hair you should be ok. Moisten a cloth and wipe the fur afterwards to get the outer bit off and away from Mom and the other kittens noses. Use something like a plastic Ketchup dispenser with the spout or tip in the cap. It is fine enough it may simply run out when you tip the container.
This seems like a lot to do just for fleas, but it requires some effort. And you can become the resident 'flea expert' among your friends.