all alone...

It won't kill her to be alone, but she won't be very happy either. I'd get another hen so she'll have some company.

 

You'll have to get her a friend eventually but if you give her lots of attention, she will be ok for a short time. I remember a time where I had a chicken sleep in the house because he would come knocking on the door to be let in. Well, his girls were always outside in the normal pen, but it got broken into and all the birds were lost. The roo that was in the house was very upset for the two months he was alone in the winter and would just stand outside by the main pen all day waiting for his girls to come back... they never did but when I finally got him some new ones, he got a lot happier and started to run around and eat stuff rather than just stand on a brick all day and come back home at night.

 

A hen might do OK, but a rooster never does in my experience. Give it a short trial and if she pines get another hen. I have had several hens that could care less for company in fact wander off to be alone, and some that totally loose it when out of sight of the whole flock. Most are somewhere inbetween. I agree human company can be the bridge.