Reasons you need to watch her closer around hatching time is a new broody may not know what to do with her chicks. I've had broodies who only knew to set in their space and when hatching time came didn't give the chicks enough room to hatch under her, smashing the eggs shell onto the chick...
I have hatched using a broody hen and an incubator at the same time. However, it was not staggered. They were all set to hatch on the same day. When they were all hatched I let the broody raise them all.
To answer your question, you can leave the chicks with her that hatch the same day...