Question on broody hen -

[hedgehog]

She is very dedicated and has been setting a few weeks. the problem is that other hens have been sneaking eggs into her nest and stepping on and breaking some. I don't know how old the eggs she's setting on are, and the shells are pretty dirty.

I can easily move her to an isolated nest on clean straw and stick some fresh eggs underneath her. That worked for me with another hen. I don't want to do it if there is any chance of her hatching the eggs she has now. Am I safe to assume that if the shells are dirty, the chick inside is dead?