Hen difficulty breathing after being piled on during dog attack

Hi everybody,

My poor 7 month old girls got attacked by our neighbor's dog last night. 2 of them died in the coop, being stepped on and piled up under the others in one corner. 1 is still alive but breathing heavily and seems to grasp for air. She doesn't have a visible injury but she may have her lung punctured or some internal bleeding. She is laying in a nesting box since it happened and is not moving.
Any recommendations on what to do? Could she heal? Or should I slaughter her to end her suffering . They were closed in coop, the dog ripped the old door at the bottom.
Thank you, hope everyone has a nice Christmas.

 

Thanks EggyJoe! I'll put her secured in a shed for the night and see how she's doing tomorrow. That gives me some hope