Katharine was married three times. Her first marriage was to Agnew Hunter Bahnson on July 5, 1941. He died in 1964 in a plane crash. In 1971 she married John de Bragança (September 7, 1912 - March 12, 1991). On September 10, 1994, she married John G. Johnson.

She graduated from Salem College in 1941 with a Batchelor of Arts degree. She was president of Salem College's "Friends of the Library," the Winston-Salem Arts and Crafts Association, the Winston-Salem Arts Council, the Winston-Salem Junior League, the Winston-Salem Gallery of Contemporary Art, the Winston-Salem Symphony Association, the North Carolina State Art Society and the Twin City Garden Club. She was the Southeastern director of the Association of Junior Leagues of America. She was vice-president of the National Repertory Theatre Foundation of New York. She was on the Board of Trustees of Salem College and Salem Academy, and on the Board of Trustees for the Winston-Salem Symphony Association and the Piedmont Festival Board. Governor Terry Sanford appointed her to determine the feasibility of North Carolina School of the Arts in Winston-Salem. She was on the Blair House Board of Directors and Fine Arts Commission in Washington DC and on the National Board of Blair House Restoration. She was involved in the restoration of the Salem College Gramley House and the reception room at Salem Academy and the entire Graylyn Conference Center. She was a member of the Friends of the Kennedy Center and Membership Chairman of the Southeastern zone in Washington, DC. She was also on the planning and coordination committee for the Stevens Center. She received the Winston-Salem Arts Council Award of "Outstanding Service to the Community in the Field of the Arts" and special citations from Wake Forest University and Salem College.