Pratt was the daughter of Harvard-educated attorney William J. West, who served as the Minister of Justice of New Brunswick from 1952 to 1958 and Katherine West (born MacMurray). From as young as the age of 2, Pratt was intrigued by the relationship of light meeting a subject and started taking paint lessons by the age of 10. She had a younger sister, Barbara West Cross. She was strongly influenced by her maternal grandmother, Edna McMurray, who was the co-founder of the first IODE chapter in New Brunswick and served as its activist president for over 20 years.