Hi everyone, I'm posting a final (and very sad) update.
We made the incredibly difficult decision to euthanize her on Thursday night, three days after the attack. Ultimately, we were concerned she would never regain full mobility (particularly the ability to support her head and/or body on her own) and that she was suffering in her current condition and in isolation. It was difficult for me to not continue treatment a bit longer just to see... but the pace and extremely limited improvement over the three days made us deeply concerned we were prolonging her suffering and she'd never fully regain a good quality of life.
The treatment of administering 1ml nutri-drench and egg yolk (alternating each time) via dropper + 10 ml water 3x a day definitely had a positive impact on her strength and alertness... and it was apparent she was no longer in shock by the second day. Her mobility remained mostly limited to the one side of her body... I had become more hopeful when her left eye started to open, but we realized it had likely been sealed shut from blood/fluids.. and she still could only move her neck in one direction and was not supporting her head or body at all. I even took her out by the other girls to see if hearing them would help "re-awaken" any nerves, but there was no improvement.
We decided to perform the cervical dislocation method to euthanize her after reading a number of articles on the web that suggested it was the most humane method. Emotionally tough, but very quick and effective as the articles described. And to be honest, seeing her at peace after three very hard days of struggle (and limited improvement... fearing she would never fully recover) made us feel like we made a good decision.
While there's no turning back from this decision, I would be very open to hearing thoughts on other treatments to try/euthanizing methods if we ever find ourselves in a position like this again. Our biggest lesson learned is to confirm that they've roosted ASAP, particularly on a windy day! But I know attacks/accidents/injuries can happen from many other things.
Thank you all for your words of encouragement, support, and helpful advice. While we are extremely sad for this loss and miss her dearly already, I'm always grateful to learn from these tough times.
Thanks again.