How did the wax repair work?
(on a different thread)
maybe thats an option?
would a little saran wrap on the area of the crack (over the moist paper towel) help
I personally wouldnt let a 4 yo handle something as fragile as a developing egg but...like missprissy said, a warm wet towel is all you can do now. just make shure it stays wet.
As sad as things are perhaps this is a good beginning lesson for her. Maybe she won't be so ready to help without permission and guidance if she knows she can endanger the life of the chicks.