Depends. Do the other hens leave her nest alone or do they still try to lay where she is brooding? If other hens are forcing the broody off the nest so that they can lay there, it could be a very big problem come hatching time. Piped eggs could get broken, hatching chicks could get injured from so much activity from the hens.
This is the biggest reason why I prefer to put my broodies in a dog crate while brooding. They are still with the flock, but the eggs hatch without other hens getting overly curious and causing problems. At the first signs of hatching, the kennel door is shut. Once everyone is hatched and ready to be up and about, I open the door and let momma hen do her thing.
