I would adore that. Usagi does have a knack for befriending very lonely people who shut out the world, so if anyone can do it? She could. Getting Winter out of Fayren is the tough part, as she's very focused on training her soldiers, but she does act in the case of emergencies, and sometimes moves into the other cities on her day off (Friday).

Maybe Usagi can think she's "helping" Winter get out more by signing her up for Minako's future date auction. :D