When chicks start hatching they need to be blocked in with the broody hen and food and water and block others out while her protective hormone and instincts and the bond grow. It is not at all uncommon for new hatchlings to accidentally get out and face brutality and not yet know how to get back under mum. The confused mum may be pecking all around... I would NOT currently accuse her of being a chick killer. I have seen other hens cause so much confusion to make the mother hen a raging lunatic! Once the mom calms down she will continue clucking to the eggs under her. Getting to know their voice and them hers. I have seen mum's peck early hatched chick to tell them get back under me as well. So ya gotta pay attention and be vigilant. Broody's aren't just a set it and forget it type deal as some would lead us to believe. It is a lot of work for the keeper as well. At least for me. Some people completely separate the broody from the flock, I don't... but I do have to provide protection the first couple days until mum is ready to come off the nest.
Keep this chick under the lamp while others are hatching and long enough to see if it will survive. If it does then it will be able to be tucked back under her in the next day or so. If you feel the need, then collect all who hatch and tuck them back in at the same time. Usually early evening after dark, so she can feel the movement under her all night and hear their voices.
Hope your baby makes it. Your hen is a beauty!
