Who is Miss Staverton from Tales of Henry James: The Texts of the Stories, the Author on His Craft, Background and Criticism and what is their importance?

Miss Staverton lives in a modest house on a small street in New York. She is carefully frugal, and manages to live on a small inheritance. Like Brydon, she is a devotee of arts and culture, who has pursued a life of the mind rather than marrying and having children. Still, she is devoted to Brydon, whether he is a dreamer or a businessman.