With food fetishes, logic has nothing whatever to do with anything. However, you might tell sis that bloody eggs, or meat spots, have nothing to do with whether or not the egg is fertile. And as for finding a half formed chick, as her how she thinks this is going to happen if the egg is not incubated. Tell her you would really like to know, because it would be so much simpler if you could get baby chicks without the bother of incubating them. Then you might send her to someplace like Trader Joe's, if they are in your area, or a health food store or even a supermarket that carries fertile eggs (some do) and have her buy a dozen fertile eggs from there. Then ask her to show you how many half formed chicks she got from those eggs. Tell her inquiring minds want to know.