She probably won't survive if you don't splint the leg, I'd do it as soon as you can, you may have to cut the stick to make it the right size for the Leg, just guessing a Popsickle stick would work for it, then I'd put her in a cage or box by herself inside and keep her warm that should help with any shock she would have, you could also try putting some electolytes in the water to help her system for shock. There was something McMurray sold for those Cornish Rock Cross chicks that was put in their water for their rapid growth, I can't remember what it was called, it was some kind of a Booster, I'd try getting some of that for the water for her while the leg is healing to hopefully help to speed its recovery, they gave it to the Cornish Rock Cross because they grew so fast and their legs would break, so I think it might help the Hen, just a thought.
Victoria