We had a hen that died yesterday. Her fellow sister hen of the same breed has been so noisy today! Almost as if she is looking for her or calling for her. Do hens grieve?!?!
It is my understanding that they do, in a way. They certainly are aware of the change and if they were "friends" I am sure she is more aware of it.
We had a broody that we had to remove the single chick from once as the other hens were ganging up on her and the chick and she looked for that chick for days but did eventually readjust.
Give her time and make sure she has other friends (you possibly being one of them).