All the broody hens I've had here seem to want to stay on the nest all day once the chicks begin to hatch. They may also have other days when they don't leave the nest, but usually they get off at least once a day until that last day. I've even seen them eating the membranes from the eggs that have have hatched, but they don't get off the nest to take care of their own needs.
I usually try to have my broodies confined to their own pen so they're not bothered by other hens interrupting them throughout their set. I've never had a broody hatch chicks in a place where other hens could get to them. I suggest you try to move your hen & her eggs before they hatch. It's best if you can move the whole nest box, if not just try to make it a smooth & seamless transition as much as you can. It's ideal to do it well after dark, and shade the new location with towels or feed sacks to keep it dim until you're sure she's settled.