It is possible she had been eating mice or her own eggs. Is there any way that she could have "run away", but then she came back and got stuck in that one area and the only way she was alive was from what she had eaten previously? This was just a thought I had. She is most likely very weak...
Continue doing what you are doing....give her plenty of water with electrolytes and free choice food. Do you have other food besides chick food? At this point, it sounds like she needs to be on a layer feed or a flock raiser feed with oyster shells on the side to provide calcium. Perhaps give...