Since she's a stray cat you could take the kittens and nurse them till you can find a shelter to adopt them - newborns are ready to adopt at 6 weeks and shelters find them easy to place. If you don't do this, they will grow up feral, starving, and perpetuate the cycle of starving stray cats in our world. I had a feral stray creep in through the cat door and have her kittens under my bed. I kept two of them, nursing them from newborn, and adopted out the other four. I still have those two cats, Kate and Fred, featured in my flickr site, and the others grew up to be gorgeous half-angora, half-tabby mixes, non-feral, with a healthy domestic kitty life.