At an early age, Mazzante attended Penn State's Lady Lion Basketball Camp. She went on to attend college at Penn State, where she was a star member of the women's basketball team, mainly playing in the shooting guard position. Mazzante scored an outstanding 49 points and sank 9 three point shots against Minnesota during her sophomore season. During her senior season, Kelly led her team to the Elite Eight, where they fell to the eventual champions, Connecticut. She earned Kodak All-American honors three times (2002, 2003, and 2004). She is the all-time leading scorer in the Big Ten Conference with 2,919 points in four seasons from 2001 to 2004. Through 133 NCAA appearances, she averaged 21.9 points per game. She also holds Big Ten records for Field Goals (1,051), Field Goals Attempted (2,403), 3 Point Field Goals (357), and 3 Point Field Goals Attempted (1,019). She was a recipient of the NCAA Top Eight Award as part of the Class of 2005. Mazzante's Penn State No. 13 jersey was retired on December 29, 2004. She completed her undergraduate degree in advertising/public relations in the off-season while assisting the women's basketball team.