Mann graduated from Southern Illinois University with a Bachelor of Science degree in 1946. A year later she received a Master of Science from the same university. Also in 1958, she was given a Doctor of Philosophy degree from the University of Wisconsin.
Mann began her career as a statistician of mathematics department at the University of Wisconsin in 1948. Two years later she became a Sister of Charity and held it until 1981.
Also in 1960, Jacinta took a position of a director of admissions at Seton Hill College (nowadays Seton Hill University). Eight years later she was appointed an academic dean at the same college. Since 1971 she served as a professor-at-large at Seton Hill College and became a professor-at-large emeritus since 2002.