Unless I've sold chicks, they stay with mama in the flock and aren't separated. It's the easiest way to integrate chicks, because mama protects them, and they learn to be chickens as they grow.
Mary
I truly value my broody hens, and have no desire to offend them in any way.
Hens don't actually count their chicks, but rely on verbal communication (panic calls) from them.
The mama hen won't miss a couple of chicks, but I'd never remove her whole brood. She's worked very hard for them, and deserves to raise them as long as she's interested.
Mary