Who is Aunt Pie from The Book of Everything and what is their importance?

Aunt Pie is Father's sister-in-law, married to his brother Benno. She announces to the family that she has been beaten by her husband for wearing slacks. Even though she expects Father to intervene on her behalf, he refuses to do so, citing the Bible as a reason. Aunt Pie is undaunted, and intends to tell everyone that her husband beats her. Ultimately, Aunt Pie is one of the group of women who come to the aid of Mother, Thomas, and Margot by attending the read aloud club. She also brings along two other aunts, Aunt Magda and Aunt Bea.