My condolences,very heartbreaking when one of our pets die,and this was traumatic for yourself and for your girl. My chickens are pets,so i completely understand how upset you are.
Just watch your other birds for any unusual symptoms. I am thinking she may have been attacked for no other reason than one hen is being a bully,then they all start in,it is not always a case of the other birds knowing something is wrong as often there is nothing wrong with bird that was attacked,but more a case of this is their nature,once one attacks,they all join in and the attacked one doesn't stand a chance,she started bleeding and may have died from hypothermia/stress,this can definitely kill them very fast.
