Yes, definitely bring her in BEFORE she delivers so she will fell comfortable.
She is very likely to use a litter box as long as it is convienient (not to far away). She will want to protect the babies which to her will include covering up any evidence of her whereabouts.
Spaying should be 2 weeks after she WEANS the kittens.

If you cannot bring her in before the babies are born, please try to find someone who will. You may not see hide nor hair of them after the birth as she will move them around for their safety. AND if you wait too long they will not be tamable and the cycle of unwanted kittens will go on.