Who is Mrs. Montgomery from Washington Square and what is their importance?

Mrs. Montgomery is Morris Townsend's sister. She is a widow with five children. Over the course of the story, Mrs. Montgomery meets with Catherine's father and exposes him as a fraud. She tell Dr. Sloper that her brother has not only been living off of her...... he hasn't provided the education he promised her children either. Sympathetic, Dr. Sloper assists her financially.