Sister Mary Lynch, formerly Sister Mary de Porres, taught high-school math at Nazareth Academy and St. Agnes High from 1949 to 1973. She also taught four math courses at Nazareth College from 1967 to 1968.

In 1970, Sister Mary said she felt a calling to theology, religious education, and spirituality. After completing her degree in 1975, Sister went on to become the religious education director in parishes in Corning, Penfield, and Phelps, and eventually the field consultant for the diocesan Religious Education Department which covered 12 counties.

During the occasion of her 75th Jubilee celebration in 2021, Sister Mary reflected, "I’ve tried to live by one of Mother Teresa’s sayings, 'Spread love everywhere you go. Let no one ever come to you without leaving happier.'"

In 2026, Sister Mary was celebrating 80 years as a Sister of Saint Joseph.

She is predeceased by her siblings, Sister Mary Ida Lynch, SSJ, Gertrude Lynch Amesbury, Warren Lynch, Reverend Joseph Lynch, Reverend Leo Lynch, Edward Lynch, Walter Lynch, and Bernard Lynch. She is survived by three generations of nieces and nephews, in addition to many friends and her Sisters in the Congregation.