Awe, I'm so sorry to hear about Nellie. And I feel horrible for your friend, who was trying to do everything she could for Nellie. What a terrible time for your friend to go through. Birds in-general are just so fragile when it comes to Anesthesia, Blood-Loss, and just the general Stress of surgery...I hope for the day when we've finally developed a "Bird-Safe" Anesthesia; it's getting better, but far from there...
***This is actually a very good learning-experience for people who own parrots who are "Pluckers" and/or just have little to no feathers on their wings bilaterally, which is quite common. We as people don't realize how much birds depend on their wings for pretty-much ALL of their movements, especially their balance and stability...So for a bird who has no wing-feathers for balance, stability, or to simply break their fall/glide to the floor, they are essentially wide-open to all kinds of injuries from constant falling. And trying to get them to learn to use their legs instead of their wings may or may not happen over-time, but chances are they are going to have falls...So it's up to us as their owners to look at accidents such as Nellie's and learn from them, and try to take precautions for our birds that we would NEVER normally think to make...So we thank your friend and Nellie for what other bird owners can learn from this devastating loss of a family member...