Rita Rose Marie was the daughter of Gertrude Gallagher and James Anthony Slavik. Her siblings were Martha Manning, Jo-Ann Mitenko, Catherine Heller, May Sevcik, Shauna Paulgaard, Loretta, Wilfred, Leo, Robert, and Margaret Buchinski.
Sister Theresa obtained her B.A. (French and Spanish) from the University of Western ON, London in 1954. In 1961, she earned her M.A. (English) from the University of Notre Dame, Indiana. She also obtained her Permanent High School Assistant Type A Specialist (1967) and her Intermediate Secondary School Principal's Certificate Type B (1965).
Sister Theresa began her ministry as a teacher, and eventually principal in Catholic high schools in Sarnia, London, and Windsor, from 1948-1979. She enjoyed teaching and interacting with young people. From 1969-1987, shed served as a congregational leader as local superior, assistant general superior, general councillor, and general secretary. In 1988, she opened a house for at-risk teens in Edmonton, AB, part of the Boyle Street Co-op outreach program. Here she provided a safe and accepting environment for many young people. Sister Theresa was much loved by her "kids," many of whom stayed in touch, saying that she was like a mother to them, and helped them to stabilize their lives and start anew.
In 2015, Sister Theresa returned to the Sisters of St. Joseph residence in London, where she continued to be a vital presence among the Sisters. She had a capacity to accept people as they were, never being judgemental or critical. She was always ready to listen and provide a wise and humorous perspective mixed with common sense. She was unflappable, putting situations into a bigger context and saying that life was too short to worry over small things. Her wonderful curiosity enabled her to explore questions about life on other planets, life after death, and other interesting matters. She was not shy to share her opinions. She will be missed by many, especially her beloved "kids."