Who is Aunt Pratt from Pudd'nhead Wilson and what is their importance?

Judge Driscoll's sister, Aunt Pratt, is childless and widowed. Thus, she lives with Judge Driscoll. When Tom comes to live with Judge Driscoll and his wife, Aunt Pratt is thrilled by the fact that there is finally a child to care for. On the night that Judge Driscoll is murdered, Aunt Pratt is awakened by the sound of people running. She then goes into the sitting room, where she finds the twins standing over her brother's dead body. Aunt Pratt did not hear a cry for help, and she is one of the star witnesses against the twins in court.