I'm sorry to hear about your frightened hen, that is really tough for you and her. We had two roosters and the young one turned out to be very mean and caused serious injury to one of our hens, Emily. That rooster went to the dinner table and Emily was separated to heal, but as soon as we let her out again she seemed like she wanted to get back in to her separate run and shed and she had become very nervous. Within less than a day her wound had opened up again, this time thanks to the older rooster (he is not nasty but I guess her healed skin wasn't very tough).
She was separated again and is now a sort of granny to our six rescue hens (ex-caged hens) who arrived a month ago. She seems totally happy now - no rooster to upset her and she is the boss of the others but gets along with them really nicely. She likes her company and no longer seems frightened like she did. Maybe you could keep your girl separate on a long term basis but get her a buddy or two for easy company?
I'm planning on moving her kennel out to the coop so she can get reintegrated with the big flock again.
