Who is Miranda Redpath from The Diamond Age, or, Young Lady's Illustrated Primer and what is their importance?

Miranda Redpath is a quite attractive young woman who evolves from being a simple actor to being one of the most active characters in The Diamond Age. Early on, she moves to Shanghai to become a "ractor" (i.e., actor in interactive games and movies). She quickly gains a good reputation in her profession, but her involvement with Nell and her Primer eventually becomes her main interest. Miranda does not know who Nell is or even where she is located.