I know people that keep just 1 chicken. I myself is down to 1 hen now, shes 8 years old, the rest of my flock lived out their lives.
Chickens are very flock oriented and need companionship. I applaud you for considering rescuing this hen. But in order to keep a lone bird, you will need to step into the place of other birds. Spending as MUCH time as possible with her, go free ranging together, bring her down to the house for goodies, sitting in the coop and run with her, really interact with her as many hours as possible. When you aren't there, leave a radio on some quiet music during the day. Use a ticking clock 24/7 to help act as white noise.
My hen is old and probably tolerates it better, however a young bird has years to live and they need to be quality. You might give it a try however be prepared to get her a buddy? Another Polish? You might make her a house chicken? Lots of people do it. You can use chicken diapers too.
Lone chickens are not the best situation but rescuing her will give her a new life. You can always add to her if it doesnt work for her.