That is the only thing I can think of.. but egg bound hens do not poop, and they strain. If they do get poop out, it is very runny and mostly urates and liquid. It wouldn't be a lot of liquid either..It was 78 today with a nice breeze. She was on the floor of the coop which was around 72, pop-door open & people door open so nice cross breeze on the floor. It's 67 tonight but she's in the garage so it might be 70 in there. Could she be egg bound? I honestly am not sure if she's laying yet or not.
When I had my egg bound hen she looked cold, not hot. :/
Those temperatures would not cause heat exhaustion, and she should not be dehydrated if you had given her water earlier that day. Chickens won't die if they go a few hours without water (unless it is extremely hot).
If she does not improve by morning, I would say you have a cull on your hands.
