****! I had to put her down anyway. Two days after putting her and the other hen back with the flock, I found that the wound on the back of her neck wasn't just ripped open, it looked like some skin was actually missing. There wasn't enough skin to suture back together.
I suspect that my mean EE rooster did that to her because he was mercilessly flogging the other hen I reintroduced. I've got the rooster separated and living in his own temporary 4'x4' cage until I figure out what to do.