Who Is She?

Someone new has appeared and Jack can't shake the feeling that he's seen her somewhere before, North warns him to stay away from her but Jack just can't fight his curiosity. He watches her from afar for a while but he's not satisfied with that and finally decides to introduce himself only to have the girl run away, making Jack even more curious. Who is she? Why is she so familiar? Why do the guardians want Jack to stay away? So many questions but no answers at all....Yet.