If you have a brooder lamp that you can use, just dont' use a 250 watt bulb. Just use a standard bulb, should give enough added warmth for her. When chickens are stressed, heat helps. If you don't have a heat lamp, maybe an electric heating pad on low with a towel over it. You might also consider giving her warm wet food, scrambled eggs for more protein. She's going to need it, the high protein to help her heal.