Who is Grandma Mariam from Black, White, and Jewish: Autobiography of a Shifting Self and what is their importance?

Grandma Mariam, Rebecca's paternal grandmother, does not approve of her son's interracial marriage and never acknowledges her black daughter-in-law. Miriam does, however, accept Rebecca. Grandma Miriam teaches Rebecca about her Jewish heritage and family, but Rebecca never comes to understand exactly how she fits in. In the autobiography's final chapter, Walker notes that her grandmother's funeral was the only place she ever saw her father cry.