Unspoiled! The Constant: Lost

Jack says that Juliet is One of Us. Everyone else thinks she's One of Them. Juliet isn't saying either way, but we know she's on some secret mission dictated by Ben, who has manipulated her into staying on the Island for three years when she knew after six months that she wasn't any use to their fertility issues. So, who's right? Which side is Juliet really on?