Use a graphite pencil for marking. I usually use an old rabbit hutch...it has hatched many broods...
I have also had hens hatch outside with only a makeshift shelter over their heads, hens are pretty flexible.
Again good luck,
Sandie
I would think it still highly likely that she will hatch them. If you give her fertile eggs just make sure she is getting as much high quality nutrition as possible as the brooding process takes a lot out of them.
Good Luck,
Sandie