You can make a partition out of a scrap wood frame with chicken wire or just stiffer hardware cloth cut and bent into shape to rest against the front of her nest and secure it with bungee cord or wire loops over strategically placed screws. This barrier won't impede air flow but will prevent her from being bothered. Keep it in place during your flocks primary egging time and remove it after they egg so she can get out for her daily stretch. Once you hear her start talking to her eggs (probably around late day 19 or day 20) you can leave it in place to keep out nosey flock members till she hatches.
Our hens hatch in the coop most of the time, they rarely need intervention but sometimes a more timid broody just needs a bit of reinforcement...
Depending on your coop and boxes set up you can create a box out of wire and just leave an opening in one side, place the opening against her nest box. This will give her a small area to step out into for broody poos if you can't be around to remove a barrier to let her out. A wire dog cage with the door swung open and placed against her nest will do the same if you have one.
