Update. Nevermind! When I got home this evening she was back in the coop! We candled all the eggs and saw no embryos forming so we will put some in the nesting boxes to encourage laying in the desired area. Just for my own knowledge would chicks be ok in the environment she was in? Even in the cold.
What is your climate?
Putting your location in your profile can help folks give better answers/suggestions.
They
can brood in the cold, but I wouldn't recommend it.
I let one go last Jan/Feb during extreme cold and it worked out OK, but I kept a
very close eye on them and I wouldn't do it again.
Extreme temps can severely reduce any margin of error for mishaps.
Predator protection and reintegration with the flock might have been other issues with where she was.
There's lots of different ways to manage a broody hen
and the subsequent offspring(especially the inevitable males), IMO it's best to plan ahead.
I prefer to have them separated only by wire from the flock to reduce intrusion problems during incubation and assist in integration.
Then when chicks are well on their feet, eating and drinking in a creep area, remove wire barrier so mama can integrate them into the flock.
Here's plethora of techniques, examples, and experiences to browse thru and ask questions:
https://www.backyardchickens.com/t/496101/broody-hen-thread