Don't restrict her - she needs to be able to get out when *she* wants to, not just when you are there to open the door for her now and then. Rather than trying to keep her in and others out, simply mark the eggs that she is intended to hatch and check the nest daily to remove unmarked eggs, which will be those laid that day by other hens visiting the box. Leave feed and water where they normally are - a broody needs to get up and move around and having to move to the feed/water helps accomplish this. Feed/water right at the nest can also lead to fouling of the nest.
Whether you opt to separate or not is up to you - some do, some don't. I am in the don't camp and have not had any issues whatsoever with using this approach - plus it's a whole lot simpler, imo, as not only does it not require setting up entirely separate quarters, it also eliminates the issue of re-integration of the hen and integration of the chicks into the flock.