[2][3] Walsh read mathematics at the University of Oxford, where she earned a bachelor's degree with first class honours in 1954.

She became a teacher and assistant mistress at Howell's School, Denbigh, but left after three years to study numerical analysis at the University of Cambridge.

[2][3] Walsh was one of the four founders of the Nottingham Algorithms Group in 1970, along with Brian Ford, who was a Lecturer at the University of Nottingham; Shirley Lill, Lecturer in Optimization at the University of Leeds; and Linda Hayes, who was the research assistant of Professor Leslie Fox.

After her retirement, she completed an MA in Contemporary Theology in the Catholic Tradition at Heythrop College, University of London.

She also successfully campaigned for the restoration of the Tridentine Latin Mass to the liturgy of the world-wide church.