Best not to have taken her out of the flock at all...unless she was being drastically picked on.
How long has she been inside?
How cold is 'pretty cold'?
I would put her back out with the flock, in the crate if she's getting picked on.
They often don't feel so good during a molt, the pin feathers can be uncomfortable and they will isolate and rest more.
Increase their protein to help grow the feathers out more quickly.
I had 2 barebacked hens last winter ...and it was brutal winter...
....they got thru it just fine with no heat, one of them was of the few who regularly came out onto the snow in the run.
Also have a 9 mo Welsummer molting, and not laying, right now.