Be carefull, she may not accept the chicks, or they may not accept her, if they are at the feed store they have been on thier own for a couple of days at least, and may not want a mom. If they do not mesh you will need to have a backup plan to raise the chicks.
You would be better off to limit the # of eggs you let her sit on, and issolate her or the other hens will continue putting their eggs in her nest, which may cause her to move on to a less active nest box, leaving you with partially developed eggs. Plus if you do not mark the eggs and she is sitting, you will get a staggered hatch, and after a couple days she will abandon the remaining eggs in the nest, so again you should have another means for those eggs to continue to develope fully and hatch.