x2at this age the lone chick should be in a brooder box with heat lamp raising the temp to about 80degrees, you lower by 5 degrees every week by moving the light just far enough away to lower the temp to that degree on a thermometer in the brooder. . When she is fully feathered out she won't need the extra heat. you can give her a mirror so she thinks there is another chick, a little stuffed animal that she can cozy up to.
you could get the chick a buddy or two....https://www.backyardchickens.com/t/25/california-northern
