Who is Maggie from Rebellion and what is their importance?

Maggie MacDonald and Serena have been friends since they were small children. As a child, Maggie is described as a pesky young nuisance of a girl. By the time Ian MacGregor plans a ball as a ruse to gather clan members who are organizing for the rebellion, Maggie is eighteen and a beautiful, young woman. She has her sights on Coll, something that doesn't require a lot of work because he is immediately smitten. When Maggie climbs a ladder and pretends to fall in front of Coll, he quickly helps her treat her injuries and promptly asks her to marry him. Maggie and Coll remain in Scotland when Serena and Brigham leave for the New World.