I know it's hard when chickens are lost to predators, and I'm sure I'll catch heck for this, but not everyone sees chickens as pets.
I use a chain link run for my chickens. I've covered it with plastic netting. The plastic netting wasn't for predator proofing, it's to keep my chickens IN.
I use chain link kennel because we have more of a coyote problem than coon, and yes I've had coon problems before...but I've never had coons go through my wire or the netting. The coons I've had to deal with usually found their way into the coop itself, skipping the run all together.
You cannot blame them for being victims of a predator attack. Maybe they predator proofed the best way they know how? Have you asked them, "What measures have you taken since the attack?" each time something has happened?
I have a friend who's coop is pretty much fort knox, and she still lost chicks to a coon attack. Not her fault. She set out traps for that coon, and still lost more chicks to a coon attack, but no coon in the trap.
Oh, and her runs aren't covered, and her chickens were locked in the coop at night.
I don't have all of my runs covered, either. So while you are thinking that's just asking for trouble, let me remind you, predator attacks happen, no matter how tight a coop is locked down! If they want what you have in there, they will find a way in, some predators can and will chew through wood to get in.
I will also admit that I don't worry about my coops being in lock down or fort knox because I have a great livestock dog who is on patrol all night and will chase off most predators before they get a chance at my chickens....
You cannot keep her chicken without asking her first. I wouldn't stop being her friend, either, over chickens. When they get home, sit her down, talk to her, offer your help to her with predator proofing. I doubt that it's a lack of caring, most people don't ask for predator attacks.
Have you gone over in the past and offered to assist with predator proofing? Maybe she doesn't know how to go about preventing a predator from getting in?
As for a single bird being unhappy, I'd have to disagree. My grandmother kept one chicken for a looooong time, until it died of old age. It was the ONLY chicken she had, and she became a very spoiled chicken. She got all of the table scraps, chicken feed, free ranged 24/7, roosted in a tree, and got more attention from her humans than I had ever seen. She was a very spoiled chicken. Never seemed to suffer from not having other chickens around, either.
Chickens aren't like pack animals. Normally, they won't grieve themselves over being by themselves. Won't bawl like a goat if they are by themselves.