[4] As a freshman in 2015, she helped the Panthers win the PIAA championship and was named the team's Rookie of the Year.

[5][6] Mertz played one season at the University of Dayton in 2019, scoring three goals and adding two assists, and was named to the Atlantic 10 Conference's All-Rookie Team.

[5] After that season, she transferred to her hometown University of Pittsburgh; coach Randy Waldrum said the program wanted to recruit Mertz earlier, but she had already committed to Dayton.

[3] She helped Pittsburgh qualify for their first NCAA tournament in 2022, where they lost to Florida State in the third round, and set a program record with 14 wins.

[16] On July 31, she scored her first professional goal in the 90th minute of a 3–0 win against Monterrey in the 2024 NWSL x Liga MX Femenil Summer Cup group stage.