Oh man, this is "Poor Violet". She is one of my wyandottes. She was at the bottom of the pecking order and they had ripped out her tail feathers. I coated it with blue kot, and they would still bully this girl. Finally, someone suggested maybe my coop was too small; that they'd pack in there and she would ruffle some feathers, as it were, by bumping into the other girls, causing them to bully her in the dark.
Since building the bigger coop with more perches, all her tail feathers are back and she's not picked on even in the yard during daylight.