She met her husband, John Mella, at the Catholic Worker where he was doing pro bono work, and they were married in New York City in June, 1938. During the Second World War, John was a conscientious objector and, with their new family, they worked at the Easton Farm, under the auspices of the Catholic Worker.
After the war, she and John settled, first in Lisle and finally in Wilmette. Their home became a regular stop for members of the Catholic Worker, including Dorothy Day. They were also active in the Christian Family Movement.
After raising a family of eight children, Katherine taught elementary school for more than fifteen years at St. James in Highwood. When her husband died in 1980, she became involved with the Hospice of the North Shore where she was recognized as Volunteer of the Year in 1993. In later years she tutored inner city children, at Good News School in Chicago.
She is survived by eight children: Margarita, John, William, Katherine, Michael, Mary, Philip and Joseph; seven grandchildren: Jo, Dale, Katherine, Jason, Rebecca, Joseph and Nicholas; and six great-grandchildren: Bradley, Katrina, Oliver, Jacob, Elijah and Grace.