Keep her away from the other chickens when she's broody, as they will bother her and possibly her chicks when they hatch, and keep her in a safe place. Make sure she has access to water and food and actually takes it - Some will often eat as little as possible, and people often wonder if their chickens are simply missing. I've never actually had a hen go broody though, but look forward to it if our Brahmas do. If - Operative word.
I have had much better luck when they just decide where to go by themselves and disappear. All of a sudden the reappear with their family! This time I tried to move my broodies into private accommodations and they must not have liked my style because they both went off their nests. I will try again a bit later in the season. Good luck! Terri O