Who is Vanessa (Stephen) Bell from Moments of Being and what is their importance?

Vanessa is Virginia's older sister. During their lives, she served as Virginia's closest friend, ally and confidante. Vanessa was a painter, and she was reputed to have been as interested in the art of sexuality, as she was in the art of painting. Virginia describes her sister as scrupulously honest, incapable of hypocrisy, strong willed and naturally wise.