If she is broody, she's broody. Nothing you can do about it. There is a thread on here about broody hens. They may have a way that will break her. Broodiness is hormonal....try telling someone with PMS to "keep it down". LOL
Broody hens don't care who's eggs they hatch. I had a white silkie hatch 4 black chicks. She is either color blind or blaming the father for the feather colors. Not one single one of the eggs she sat on for 21 days were hers. She's back on another 4 eggs. I'm not sure who's eggs they are or even if they are fertile, but the egg I wanted her to hatch got broken by someone and didn't hatch, so I grabbed all I could find in the coop that day and threw them under the poor thing. She was walking around clucking for her chick and looking in and around the nest box. It was really pitiful. So I put 4 eggs in her box and she climbed in and got comfy. I'll see in 21 days if they were fertile and what hatches.