I think you will lose every egg if you allow so many eggs that she can't cover them all. The eggs she can't cover will get chilled and die, then she'll pull those dead eggs under her and a few more viable eggs will make their way to the outside and get chilled and die. The scenario repeats until all/many eggs are dead. I don't know if it is too late, but I think you should cull enough that she can successfully brood them. Better to have a few hatch than none.
A very experienced breeder told me to only let a broody sit on an odd number of eggs. He said that an odd number makes a round/oval shape in the nest which is the shape of a hen. An even number of eggs tends to end up being square or rectangular shaped, and the corner eggs tend to slip out from under the hen or not be covered well enough, get chilled and die. The hen then pulls them under her and different eggs get chilled and die.