Callista L. Gingrich Callista L. Gingrich is the U.S. ambassador to the Holy See. By this Author Mar 08, 2019 Women of Courage honoree Sr. Orla Treacy is a beacon of light in South SudanCommentary: The Irish nun, head of Loreto Schools in Rumbek, received the State Department international award for her courage, inner strength and fierce dedication to female empowerment.