FWIW I don't think chickens (in the least) feel pain like we humans do. I have a chicken attacked by a turkey, he pecked and pulled off all of the skin on her back, and made hash out of the side of her face to boot. This was about a month ago. I gave her a baby aspirin a couple times a day for a few days but dang it if that chicken didn't start eating and drinking on her own, flapping her wings and developing an ugly, thick scab over her back. It is beginning to peel back now, and there is actual skin beneath it. I still can't believe it.
The baby aspirin I gave after letting it melt in my own spit (eww) and sucked it out of my mouth with a little syringe, and then shot it in her beak. It really perked her up, I think it helped a lot.
So I'm saying she may not be suffering as much as you'd think.
Also, if their leg even hurts a bit, they won't use it for a few days. You'll know the leg is in bad shape if she still won't use it in a week or so. But even with that, the darn little things are so tough, I'd give her a chance.
Bring her in, keep her warm (they'll lose 10% of their body weight per day during acute healing just to keep warm), keep her in a dark, mellow room. She's in shock and this is also a vital part of her healing process. Let her stay very quiet, warm and unstimulated. Her body will do the rest, if it is at all possible.
If she won't eat or drink, syringe food mixed with water into her beak, she'll swallow it. It'll keep her going until she feels like eating/drinking on her own.
Good luck