Wow, I guess I haven't given her enough credit in the brains department. Crazy broody hens! I marked the first 9 eggs and when I manage to catch her off her nest I remove the ones that weren't part of the original group. She does this everyday. It would be fun to put up a camera in there to see how she manages to do it. Most of the hens prefer two other nesting boxes we have with are farthest away from the one one broody is in. I haven't found any damaged eggs either. Our chickens are constantly surprising me!I caught our silkie in the act of moving eggs from one box to another before I put her into her own broody box.... she rolled and pulled and rolled and at one point picked the egg up by pinning it against her chest with the underside of her beak for a quick lift. It is a wonder she didn't drop or break any, but I never found any damaged ones. After watching some of her antics I will never doubt the abilities of a determined broody to accomplish anything!
Other hens may actually be laying on top of the broody while she holds her ground and refuses to move from her nest... I have seen two hens in the same box numerous times, they can be weird sometimes, that's for sure!