Update- Not sure why she did what she did, but we have 5 survivors out of 8. She's taking care of these just as she should. I guess mother nature stilll knows best. Here's hoping they are all hens!
I am in the same position, my Black Australorp Hen has sat on 10 eggs until they started to PIP, now she is killing the chicks and eating them as they hatch. The only thing that I can think of is to watch for the PIP'ing and pull the egg hoping that it will hatch and I can save the remaining 5 chicks.