You'll find that each hen comes with her own component of broody skills. Some have been dealt a better hand than others, will do a better job of brooding. A lot of breeds that have been selectively bred to be good egg producers have had that broody instinct bred out of them. Other breeds meant for more ornamental purposes tend to be more broody. Individual results may vary. Meaning that even super-productive breeds like Leghorns & RIR may still have a few individuals retaining that instinct, while those breeds more prone to broodiness will still have their individuals who won't set well.
You'll know a hen is broody when she spends about 23.75 hours a day on the nest, taking a short break once a day to eat, drink, & take a big poop. She'll fluffle up her feathers and spread herself wide over the eggs. When you reach towards her she may growl, screech, and/or peck at you. If you feel up underneath her, she'll have a bare patch on either side of her keel bone.
Some hens seem to just play at being broody. They hear faint voices in their heads that say "sit on it!" and they may stay there for a few hours, or just a day or two, but won't stick with the job.
Check this evening to see if she's back on the nest. If not, the eggs may still be okay to eat, or at least to feed to the dog. If she is broody, you can check other threads for info on how to keep her separated and ensure greater success for her hatch.
