Thanks for the advice. I'll bring her out with the others. I just wasn't sure if I'd do more harm by intervening. This is my first time raising chickens and so grateful for this forum!
I did manage to lure her out a few days ago when the weather was nice. She even went kind of near the other hens for an hour or so before returning to the coop. Then we had two days of freezing rain. She hasn't been out since.
I have a seemingly healthy hen that won't leave the coop. I recently had to re-home my rooster because she did not submit to his mating and he started attacking her. She was pretty traumatized by it. She's a bantam and he was huge. So I had to get rid of him before he caused physical damage...