If you have the space to do that, that's great. Many people don't have the space to totally separate their new chicks from the main flock, and it isn't really necessary to do so. If you can give the momma some private space with a upended laundry basket or other privacy shielding in the main flock's area, it does allow the chicks to gather their strength to run away from aggressive hens.I really think that week separate from the flock gives them time to toughen up
Personally, if I had the space I would remove the aggressive hens from the coop to alternative space and leave the momma and chicks with the main flock. I have yet to have another hen kill a chick....I once had a juvie rooster attack a chick, but it survived. (It was spring, so I locked the rooster out in the run when I wasn't home to supervise. He took the hint and left the chicks alone after about a week; two days of which it rained all day. LOL) Why would I move the aggressive hens instead of the chicks? Because it is easier to integrate full grown hens back into the flock than chicks. Not to mention some "time out" time for the hens tends to put them lower on the pecking order upon return so they lose some of their aggressive behavior.