Maybe until you get her a few friends she can sleep inside that will help her feel secure and also relieve your mind that she is safe.I have looked in my area for an older duck but i may need to broaden my search to a few different locations.
during the day she is fine. We have her in a fenced in area with her pool, food, and water. Plus there are eyes on her almost constantly.
Did you look here on BYC we have a re homing thread and buy sell trade thread.