Safest is to seperate. It is hard to say for sure, they might be fine or they might not be. I would seperate for the hatching process at least. Mama hens get very protective of their chicks, and the chicks could get trampled in any arguments that go on between hens.
I keep my mama hens with chicks seperated from the flock for 2 weeks then let them slowly go back, although they will continue sleeping separately from flock until mama hen decides she has had enough and goes back to roosting. I just have them seperated with plastic mesh fence, they can still see each other and see the chicks. This is just a safety precaution. I have let hens with their chicks back to the flock in as little as a week, and some people let them stay the whole time.
Since this is her first time and your first time with broody hen, I would seperate but let her still see her flock mates.