Who is Betsy Goodman from Lisa, Bright and Dark and what is their importance?

Betsy is fifteen,bright and well-adjusted. She loves school and enjoys being with her friends. Betsy describes herself as average looking and medium in height with dark, straight shoulder-length hair. She has large brown eyes and wears glasses. Betsy's main ambition is to get married and have a family. She believes that she would be a very good wife. Betsy sees herself as average but still rather interesting.