If you keep her separate the whole time, and then wait until the chicks are 4-6 weeks, it is rather a wreck. She is a stranger to the flock, she is starting to wean the chicks, and all of a sudden is fighting for her position in the flock. Chicks are on their own hook, and the whole thing is a wreck.
The broody hormones, generally up the broody hens position in the flock. So mixing her in the flock is good for the future reception of the chicks by the flock. I leave mine in the nest of her choosing, and for the most part, she is in a trance while there. Every three days, I get her off and out she stomps to terrorize the layers. Now I am sure she gets down herself every day or so, but I like to sneak a peak at the eggs and make sure they are the right eggs.
Then when she hatches, she eventually brings out the chicks to the flock. They are already giving her a wide berth, and while they think she has some strange life forms following her, they tend to keep their distance. Generally a chick does get too close, gets a peck and screams - which turns the broody into this giant tornado puff ball,... and well everyone toes the line.
My broody hen, tends to stay on the edge of the flock with her chicks. Works a treat.
Good luck