That's rough. I used to work in field biology and when we had to euthanize birds (non-native eradication) the biologist I worked with found the most humane way was "chest compression". He had been doing it for years, many different ways and felt this was best, it's probably what I would do too. Basically, if you put pressure on the chest to prevent it from expanding they can't breath and they just pass out and die. It doesn't take too long and it doesn't really take any pressure, just a firm hold and you can hold her and pet her while she "falls asleep". It sounds horrible, I know, but is there really any good way to do it?
~kim
~kim