Thanks everyone. If she does end up having her kittens downstairs, can I move them? Maybe my Dad can move the litter box in that room and put her bed in that room. He can also put a door on the basement, too.

Once it warms up, like March, we will have to move her back outside. So she's got to be spayed. I've got VERY bad allergies to cats so I will just have to put up with it for the winter.