[1] A dependable and versatile utility, Horstman excelled as a pitcher and catcher in the All-American Girls Professional Baseball League, being also able to play at third base and all outfield positions.
At 16, she was invited to tryouts for the All-American Girls Professional Baseball League, and signed a contract for $250 a month to play with the Kenosha Comets before the 1951 season.
Briggs belted a league-lead nine homers, while Joanne led in average (.346) and Betty in RBI (81) and stolen bases (80), but Fort Wayne lost for the third consecutive year in the first round, now with the Kalamazoo Lassies, 2-to-1.
Once more, Joanne Weaver led all hitters with a remarkable .429 average and a best-ever 29 home runs, while her older sister Betty hit .352 with 14 homers and 54 RBI.
In Game 1 of the AAGPBL Series, the Kalamazoo Lassies defeated the Fort Wayne Daisies 17–9 behind a four-hit, seven strong innings from June Peppas, who also helped herself by hitting 2-for-4, including one home run.
Pitching star Maxine Kline, who had posted an 18–7 record with 3.23 ERA for the Daisies during the regular season, gave up 11 runs in six innings and was credited with the loss.
[9] When the league was unable to continue in 1955, Horstman joined several other players selected by former Daisies manager Bill Allington to play in the national touring team known as the All-Americans All-Stars.
Besides Horstman, the Allington All-Stars included players as Joan Berger, Gloria Cordes, Jeanie Descombes, Betty Foss, Mary Froning, Jean Geissinger, Gertrude Dunn, Maxine Kline, Dolores Lee, Magdalen Redman, Ruth Richard, Dorothy Schroeder, Jean Smith, Dolly Vanderlip and Joanne Weaver, among others.
She later joined the Franciscan Sisters of the Sacred Heart religious order for five years, to become the first nun in the United States to earn a Bachelor of Science degree in physical education.
For the next decade, she taught physical education in Illinois, Indiana and Ohio before returning to her hometown of Minster, where she initiated girls sports programs, including volleyball, gymnastics, basketball, track and field, cross country and softball.
Ending up 25 years in Minster, she moved to Los Angeles, California, where she oriented a clinical social work method to the sports area.
[11] Horstman has been named Midwest Athletic Conference League Coach in all sports numerous times, and has been inducted in five halls of fame in baseball and track.