I have a broody sitting on eggs right now and I have left her in the same coop with the others. I separated her with a little bit of fence thing so the other hens would stop laying in her nest box.
I'm going to keep my eye open to make sure she is able to protect any baby chicks she hatches out and then it should be fine.
If you have separated totally, you might need to wait till the chicks are older..... I'm not sure.
I just added baby chicks to my coop - chicks I hatched out, they were 8 weeks when I added them. I put their brooder box in the coop, with a hole cut so they can get in and out, and I have a section of the run fenced off with a small hole so they can get out of the way if needed.... so far so good - I do have bantams, and the bantams can get into the safe zones..... in fact one laid an egg in the brooder box. But with the safe zone's the babies are doing ok.
I also put water and food in their safe area - so they don't need to fight for food.
Good luck!
