ive seen chickens come back from some pretty horible things like this and live happy lives afterward. personaly, i think you should try to save her. it is going to take a LOT of time and care, but its quite possible for her to pull thru. for the pain, baby asprin. i would cut the skin off now, while shes still in shock cuz if u try to do it later, she may freak out, this will raise her blood preasure, and it would bleed more. verry stressfull. make sure she has somthing soft and CLEAN to lie on. but try to lay her head on something solid, because if a cloth or towel sticks to her wound, it would hurt a lot to peal it off. make sure the wound is clean, this is a critical time to prevent infection, soon after the incident. if you see any specks of dirt, try to gently clean them out with a cloth soaked in warm water. is she shivering? keep her in a dark place. keep us posted.