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

Mrs. Lavinia Penniman is Dr. Sloper's oldest sister. She comes to live with Sloper's family after the death of his wife, taking over the care of his young daughter. Later in Catherine's life..... when the boys come around, Mrs. Penniman lives vacariously through her niece's activities. Unfortunately. she becomes too involved...... causing difficulties between herself and her niece.