Some people separate the broody from the flock and some don't. People are successful both ways and there are potential risks both ways. I think this thread is a good read for you. It talks about both ways and what you need to do.
Isolate a Broody? Thread
https://www.backyardchickens.com/forum/viewtopic.php?id=213218
If you isolate her, the biggest risk is that she might break from being broody when you move her. There is some inconvenience to you in that you have to feed and water her specifically and probably clean out the poop. I agree with Tuffoldhen. Move her at night and lock her up where she cannot go back to her old nest and the other hens cannot get in to disturb her. I find it helps if the new nest is kind of dark. I suggest using eggs you do not want her to hatch or fake eggs until you are sure she has taken to the new spot, then give her all the eggs you want her to hatch at one time. Make sure she is protected against predators in the new area.
If you choose to not isolate her, you need to clearly mark the eggs you want her to hatch (I use a sharpie and draw a couple of rings around the egg so you can clearly see the marks no matter how the egg is turned) and check under her at least once a day to remove any new eggs.
Some of the risks of not isolating her. When she gets off the nest for her daily constitutional, another hen might lay an egg in her nest. Since you are removing them daily, that is not a big deal. But if another hen is on the nest laying when she gets back from her constituitional, she may get confused and go to a different nest. The hatching eggs can cool off and die. I've never had this happen, but some people have.
Sometimes another hen wants to get in the nest and lay with her. The broody may not want her in there, in which case some eggs may get broken. Or she may let her in but with two hens tight on the nest, the eggs may get damaged. Again, I've never had this happen, but some people have. I do think this is fairly rare. I've never had an egg damaged under a broody.
Something else that I think is extremely rare. I have never seen it but it has happened. Sometimes another hen will try to kill the chicks under the broody. Usually the other chickens leave the chicks alone or, if one gets too curious, Mama strongly defends her babies. They are living animals with their own personalities. You can never be absolutely sure how they will act.
I now do not isolate a broody but I also do not argue with anyone that does. With some people it is personal preference but some people also have experience that with their flock, one way or the other is the best way to go. Good luck however you decide.
