Often times my free range broody prone hens will lay eggs away from the coop so they can set on the eggs without the drama of the coop. I agree that she is probably thankful for the isolation and I would not worry about the space until after the hatch as long as the chicks can get to the water. It is possible that you will not be able to tell when the eggs start to hatch and you could have several little ones before you know it.
There is nothing better than watching a new mama hen with her babies. Also, it has been my experience with Bio-Bators that mama may want to keep her brood away from the rest of the flock for a few days to weeks depending on her place in the pecking order. I usually would set up a small pen outside of the coop for mine. Initially I worried about the cold, but as long as they had shelter from the elements, I never lost any. After a few days I would leave the pen open during the day and only close it up at night. Eventually, Mama would introduce the chicks to the flock.
