Adding to that:
First, if you DO leave her where other hens have access to the nest, you need to mark the original eggs, so you can remove newer ones.
Second, there are risks to the eggs... I've twice let hens keep eggs they decided to sit on when something stopped me from collecting eggs for several days. Two years ago, there were 6 eggs involved, and a second hen went broody and decided she was going to sit on the eggs too. 4 of the eggs got broken; it was fairly early on, so I just found eggshells and some bits of eaten up yolk.
This year, I let a broody keep some eggs she started sitting on when the chicken house got snowed in. Halfway through, I found a broken egg and dead chick, with a fresh egg on top of it, covered in yolk and blood. Next day, I found the broody sitting in the wrong nest. Consequently, some of the chicks died in-shell from getting cold, and one of the two that managed to hatch (they'd been towards the front of the nest and got some sun) was too weak to survive. The lone survivor had a dark brown eggshell, which I think is what saved it.
To put that in one-sentence terms of the risks:
1) Another broody may try to join in, and if the hens squabble about it, eggs can get broken.
2) If other hens lay eggs on top of hers, the ones you're trying to hatch can get broken.
3) If another hen is laying an egg in her nest when she comes back from eating, she may decide to sit on fresh eggs in another nest box, leaving the developing eggs to get cold.
Editing to add: First time around, I waited until the eggs had hatched to move the family into the the small isolation pen I keep inside my larger chicken run.
This time, after the broken egg and finding her in the wrong nest, I waited until she sat on the eggs again (which she did within a few minutes when I took away the fresh eggs she'd switched to). I then picked nest box, hen, eggs and all, and moved the whole shebang into the safe pen.
I was running a risk it would upset her & she'd stop sitting, but she's super placid so I knew it wasn't likely.