Thanks, everyone. I had been told by several people that it would not be a problem, that even a low ranking hen would stop at nothing to protect her chicks. So, I allowed my broody hen, second lowest in a flock of 15 chickens, to hatch some eggs.
However, when the first chick hatched, I noticed other hens kicking her out of the nestbox so they could use it to lay their eggs. Afraid the chick would be trampled, I moved the mother and eggs to a separate pen.
The three chicks that hatched are now around 4 wks old, and they and mother have been gradually re-integrated into the flock. Mother does try to defend them from most of the other chickens, but will flee from a couple of the top hens. So far, those top hens do not seem interested in hurting the chicks - they seem to just want to let them know who's boss. But if they wanted to kill them, it looks to me like Mom would not put up a fight.
Anyone else have experience with low ranking hen raising chicks within a flock?