I would go ahead and euthanize her. Even if you got the electrolytes into her, her organs wouldn't metabolize it. She will likely die in a couple hours or sooner.
Your hen appears to be dying. She may have experienced serious hypothermia from extended exposure to the cold.
She may not be conscious enough to drink, but if you can get some warm sugar water with electrolytes into her, about half a cup if possible, she might revive.
You would need to tube...