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.
Lady McCoy's palace (left) is the cause of the problems befalling the people of Kolima.