Lady McCoy is the wife of Lord McCoy and the de facto "queen" of Bilibin. She is quite self-centered and accustomed to being showered with gifts. Even though in McCoy's Palace she has a bedroom separate from her husband's, she commissions a second palace of her very own to be built right next to the normal one. Although this enrages Tret, a sacred tree in the centre of Kolima Forest and provokes him to curse the residents of Kolima, Lady McCoy does not stop in her quest to have a new house, indeed she actually accuses Lord McCoy of loving the tree more than her when he orders construction halted.
As of Golden Sun: Dark Dawn, Lady McCoy is rumored to be the one actually ruling the country of Bilibin, instead of her husband.