Hen attacking other chicks

[Aithon]

I haven't found anything on this, so I thought I'd ask here
For context, I have 7 chicks, 2 are being raised by a hen, and the others were from a feed store. They're all about 5-6 weeks old.
I've had the store chicks for 3 weeks but they weren't introduced to the other chicks until last weekend.
They were moved outside 4 days ago and are sharing a coop with my 2 older chickens with wire dividing it into 3 sections.

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The mother hen is very determined to attack the store chicks, she'll pace the wire in between them and try to peck any chick that gets too close. The chicks don't even care at this point, they just ignore her. All 7 chicks have officially met and get along just fine.
I thought it might be because they look like other hens to her (she's a bantam, the store chicks are standard size), but she hasn't gone after my other hen or my rooster, it's only the chicks.
I want to be able to let all the chicks interact with each other more but I can't just keep the hen locked up away from her chicks, so any help is appreciated.

 

[oldhenlikesdogs]

Be careful. Last year I had a bantam hen that was killing other chicks. It's the first time I've seen one be so vicious and protective of her own.

It's normal for adult birds to peck at chicks, but if you see excessive attacking take it seriously.

You can either keep the chicks separately longer, or remove the hen for a long while.