Awww, I'm so sorry for your birds, your son & for you too. That sounds like "opossum" to me, they like to eat eggs and will do that to setting hens in order to get to their eggs. If it was a raccoon it would have probably eaten the hens instead. Opossums tend to attack heads & faces, probably when the hen is defending her eggs the opossum bites back.
Post about it on the Emergencies section, show photos if you can. Certainly there have been cases when chickens make remarkable recoveries, and this may not be as bad as it seems. There's a lot you can do by just cleaning the wounds, applying antibiotic ointment, and keeping the bird in a warm, dark, comfortable place.
But you may have to help end her suffering if it's so bad that she doesn't show improvement soon. Perhaps there is someone you know who would do it for you if you cannot bear to do it yourself. If I were closer I'd help your birds Cross The Road if they needed that.
My husband now thinks the same thing. He just went to town to buy a trap to see if we can catch whatever is doing this. I went out this morning after my original post to find that whatever had gotten in now got my last silkie & my 5 year old was with my & was devastated. The tiny hole above the door to our run is the only possible way we can find for the predator to get in. My husband is going to wait to close it in to see if we can trap it. We are down to our only chicken which is our white EE Foghorn. 
Thank you for your sympathy. I truly appreciate it. Please cross your fingers for us that we trap whatever it is that is doing this... Poor Luna passed away in her sleep while I was holding her a little bit ago, she looked so peaceful & at ease.
Loving life as a wife to a wonderful man (my electrician), and a mommy to 3 sons (5,2 1/2, & 1 year old), some cats, a dog, 3 horses, a ton of cows, 1 beautiful Lop Ear bunny rabbit, 1 white EE roo, 3 EE girls, 2 Olive Eggers, & 2 black/split to lav (I think) americaunas!!
Loving life as a wife to a wonderful man (my electrician), and a mommy to 3 sons (5,2 1/2, & 1 year old), some cats, a dog, 3 horses, a ton of cows, 1 beautiful Lop Ear bunny rabbit, 1 white EE roo, 3 EE girls, 2 Olive Eggers, & 2 black/split to lav (I think) americaunas!!
