I don't have a whole lot of experience with Broody hens, but do have enough where I have seen where the bigger eggs seem to get broken by the hen easier when there are eggs of different sizes. This is not mixing bantam eggs with regular eggs, this is just eggs of different sizes.I am sure that she can do it and you will get some to all of them to hatch, but don't be surprised if you lose an egg or two as she adjusts her weight and body on them. A broken egg or two isn't necessarily uncommon, though, even when the eggs are all the same size.