[1] Fasenmyer grew up in Pennsylvania's oil country, and displayed mathematical talent in high school.
For ten years after her graduation she taught and studied at Mercyhurst College in Erie, where she joined the Sisters of Mercy.
She pursued her mathematical studies in Pittsburgh and the University of Michigan, obtaining her doctorate in 1946 under the direction of Earl Rainville, with a dissertation entitled Some Generalized Hypergeometric Polynomials.
These would be further elaborated by Doron Zeilberger and Herbert Wilf into "WZ theory", which allowed computerized proof of many combinatorial identities.
Fasenmyer is most remembered for the method that bears her name, first described in her Ph.D. thesis concerning recurrence relations in hypergeometric series.