You have two different basic options. Isolate the broody or let her hatch with the flock. There are risks with either one but most of us are successful whichever way we go about it.
To isolate the broody, build a predator proof pen big enough to hold a nest, food and water and some spare room so she can go poop. Make the nest pretty dark. I even suggest making it so you can lock the hen in the nest itself. Make that pen secure so the hen cannot go back to her old nest if she wants to.
At night after everything has settled down, move the hen to the new nest using as little light and commotion as possible. Lock her in the new nest with a few expendable eggs or fake eggs. Leave her locked in that dark nest most of the next day, just letting her out a little before dark so she can eat, drink, and go poop. She might not choose to come off the nest until the next day. Remember she is locked in that pen and cannot go back to her old nest. The risk is that she will not accept the new nest and will break from being broody. Since you have eggs coming, you might want to let her out so she can go back to her old nest if it is obvious she is not accepting the move.
If you let her hatch with the flock, mark all the eggs you want her to hatch (unless they are a different color. Then it doesn’t matter) Then every day after all the other hens have laid, check under her and remove any eggs that don’t belong. As long as you don’t skip a day you can use those eggs.
Good luck whichever way you choose.