Sourland is correct. Many breeds have broodiness bred out of them. If you are in the business of eggs, you don't want a hen to go broody as she will stop laying. None of my RIR's are broody, but my white leghorn's are, so I have had them hatch duck eggs when the mother duck would stop sitting after 2 weeks. The leghorn sat for 28 days (a week longer than chichen chicks) and she raised her own brood of ducks.
You also want to make sure she has a quiet area to sit, so make sure there are other nesting boxes if you have other chickens. A brightly lit area will discourage sitting.