Hey Poot. Is your house infested, or just mama cat? If it were me, I would bring out the big guns. There's several natural things you can do to get rid of fleas, but most of them are for management/prevention or just a small flea problem. Since she's due so soon, I would bathe her again with flea shampoo, and use a flea comb to get the dead ones out of her fur. Wash everything that's washable, and put it somewhere else in the meantime. Close your cabinets and put everything away that is on your counters. And bomb the house. Go out for the day. When you get home, put a fresh bag in your vacuum (or empty out your canister) and vacuum really, really thoroughly. Upholstery and mattresses too. Empty out the canister/throw out the bag immediately. In a couple of days, the eggs that were missed the first time will start to hatch. Bathe mama cat again and comb her with the flea comb. Now I would use diatomaceous earth OR Borax overnight and vacuum in the morning. You can also dust mama cat with baking soda. Put a flea collar inside your vacuum and empty it every time you vacuum (preferably a couple of times a day).
I would dust the yard with DE in shady areas and in areas where there is longer grass. You may be bringing them in on your clothes, and your cat can get reinfested even if she never goes out. There's recipes for homemade flea collars using essential oils, but they aren't recommended for cats. But you can try feeding 1/2 a clove of garlic or a 1/2 teaspoon of yeast everyday.
You can try scattering pieces of wet newspaper on your floor overnight, put a few drops of cedar oil on them. The fleas will be attracted to it, and you can gather the papers, fleas and all, and throw it away in a garbage bag.
If you decide to use diatomaceous earth, be sure to get "FOOD GRADE" and not the stuff that's used in pool filters. Pool filter DE is high in silica dust, and is dangerous to breathe.
You can make a sachet of dried chamomile for her sleeping area.