Orpingtons are pretty fluffy, so if she is out of draughts she will be fine as you are doing. To help you can put some vaseline on her comb and wattles which reduces heat loss by evaporation. Straight comb chickens are prone to frostbite at the tips if the temperature gets much below freezing. Older birds are less able to stay warm as they are less active so just keep an eye on her and make a daily judgement of her condition. We often bring older birds in at night, just to be on the safe side.