I've had Mom & chicks go right in immediately after hatching out in the run with my Rooster and other hens, and all was fine. I've also had to separate a hen when she wanted to fight all the other hens (but nobody was bothering her chicks & I just set her up in an adjacent pen and the chicks could still run through and visit everyone else, but she couldn't. {I will say, initially, it is a frightening thing to watch, for the first time, a 9 lb rooster bend down and get cheek to cheek with a newly hatched chick, looking at the chick and you not knowing what he'll do. My Rooster then tried to give them food.}
It seems to matter the "rank" of the hen (the higher ranked the better because the others won't touch her chicks; my #2 ranked hen would not let any of the other hens eat while her chicks were eating except the top hen who did what she wanted but did not pay the chicks any mind whatsoever.). However, experiences are going vary widely on your question as the other comment said her hens killed the chicks. Flocks are all different. Set-ups are different.
First, make sure, if mixed in with the flock, there is plenty of room and places for mother hen to go with her chicks out of the way and second, make sure you spend the first couple of hours out there watching them to see how it is going to go.
I am about to have two hens with broods at the same time, and I am going to have to be out there because I don't know how it will work (or won't work).