Who is Belinda from Geography Club and what is their importance?

Belinda is a girl at school that tries to join the Geography Club. She accidentally overhears that the club is really for gay students when she walks into a meeting late. Belinda tells the group that she hides the fact that her mother is an alcoholic and understands having to lead a secret life. She promises to keep their secret and continues to be a member, even though she is straight.