Hen attacked hatching chick?

[BlueMoon-N-Farm]

Alright so this was a new one for me, my hen attacked her one little egg that she had been incubating as it began to hatch.
I found it half way zipped with injury's to its face.
Now I have never had a hen do this before, so my question is:
1. Why? Was it because she just didn't realize what was going on from being a first time broody?
and 2. Do I dare let her hatch anymore eggs?
She is still trying to hatch her sawdust out there and i'm not quite sure what to do with her now?

 

[troy4]

The chick could have been sick or she wasn't recongnizing what was going on.