I'll be the first to say it: you should have spayed her 6 months ago, and you'd not be worrying about this now. I don't know anything about you, your cat, or financial situation, but spays are inexpensive and often free.

Sorry to sound blunt and rough. I volunteer for a cat rescue and foster kittens in my own home at my own expense.... and it irritates me that somebody doesn't take the time to care enough about their cat to spay her. Then it irritates me that once she is pregnant they know nothing about what to do. I'll tell you what to do: GET HER TO A VET! She needs prenatal care just as a human does, and the vet will help you prepare for the kittens' arrival.