I discovered tonight that I have a missing chicken and found one dead. There are feathers all over the coop and outside of the window.... Her body was picked clean. [no] head. No blood. Just feathers, wings, legs and feet, and bones....
Without a photo it is hard to know but a coon will often use its finger and hand strength to devoir a chicken similar to how a human would pick and eat berries off the bush.
As a general rule however any chicken that is killed and eaten and the skeleton is still intact or articulated was killed by a bird of prey.
The fact that you found your 2nd hen and that she is alive is more evidence that the culprit was a bird of prey. Hawks and Owls begin feeding before the victim is dead.