What I meant to say is sounds like she's in shock. I would give her a chance to come out of it.
I wouldn't personally feed by tube if it's her first day not eating. She won't die of malnutrition. But maybe you are more comfortable doing it than I am. Hydration is key above all else. But since this just happened today, she will likely recover without tube feeding. Shock really happens, I've seen it after attacks. If she still isn't standing, eating or drinking... I would inspect very closely for puncture wounds, near the back of the neck. They can hide pretty easily. But also pay attention to notice any swelling that might be where a bite is hidden. It's possible she wasn't got and is just that scared. Poor girl!
The door open is what has me wondering top. But sometimes they didn't close all the way and the wind or whatever helped it open? Maybe another person in your family went to see them and accidentally left it open?
I'm in the PNW too, but on the coast where it stays very mild. 18 is NOT low enough for your girls to require heat, unless they are ill. They are wearing down jackets and heat will just make them feel colder when they are away from it and give them a harder time adjusting on a daily basis but also especially if your power goes out. Most important thing in cold weather is ventilation. Moisture build up inside the coop is what will cause frost bite, not the actual cold. Moisture is exhaled every time they breath so don't forget that as a main source.
I totally think she's just in shock and patience is good. I like to give probiotics (raw, unfiltered acv in the water), electrolytes, or vitamins if someone had a major stress just to help their own system not let anything else get them down. So basically a little extra support. But not tube feeding unless it has been several days without food and more than a day or two without me SEEING them drink (doesn't mean they didn't). I had a duck get scalped by a raccoon and survive with just that, as I didn't want to cause her more harm. She did recover beautifully but the shock was apparent for the first few days. Her eating and drinking were severely diminished but I saw her making an effort.
Eyes opening is a good sign! I hope and believe you will continue to see improvement.
