https://www.backyardchickens.com/t/549832/why-would-a-mother-hen-try-to-kill-her-newly-hatched-chick
Mother hens have a sense for sick chicks. Evolution is still in play even after 5,000 years of domestication. She could be culling chicks that are sick.
on the other hand, some hens are nuts and dont know what to do. Chances are she has never been mothered herself if she was hatched from an incubator. if this is the case, she may never have learned what is required. Or she just may be neurotic. Either way, its a good idea to remove the chicks before she continues the behavior. Some hens do great for a week then start killing.
Another thing that comes to mind is lighting. We had a dog once that was a wonderful mother, fantastic dog and always very friendly. However, one day after delivering her 3rd set of pups, she went nuts and started killing them. It turned out that the 24 hour light we had on her was causing her to go crazy from lack of sleep. She wasnt getting the full rest she needed and was losing her head. After taking the pups for a few hours and letting her rest, she took to being a good mom again. If your hen is exposed to 24 hour lighting, it might be the cause. if not, maybe she needs a break.
I dont know if chickens can handle the removal of their chicks for an hour, but it might be something to look up. Maybe she needs a mommy break. Especially if its her first time.
11 is a LOT of chicks for one hen too I think. Maybe she is frazzled. Or perhaps she smells you on the chicks and its making her think they arent hers.
One thing Ive done to get a cat to mother kittens that are not hers is to put a dab of vanilla extract on her nose and do the same to the kittens. She takes them in like they are her own.