It sounds like the stress that made her pick her feathers was from living with the flock. Seems like it could only be a good thing to keep her as a house duck. Good for her to relax, good for you to get as much special time with her as possible.
Be comforted; the best we can ever do for any animal is to make sure it's happy and it's needs are met. No matter how long or short a time that may be.