Following her rookie season at Yale, she played for HC ŠKP Bratislava in the European Women's Hockey League (EWHL), leading the team in points with 25.

[4] She earned All-Ivy and All-ECAC honors and broke Yale's all-time scoring record which had stood for 35 years, graduating with 168 points in 129 games.

[5][6][7] Entering the 2024 PWHL Draft, Hartje was projected as a top-20 pick by The Hockey News because of her 200-foot play, playmaking ability, and face-off prowess.

She has also participated in USA Hockey Women's National Festivals and player development camps, most recently at the senior level in 2024.

[10] Hartje played for the Slovak national team in 2021 against Austria, Germany, and the Czech Republic after she had lived in Slovakia for eight months and established residency.

A four-time All-State selection in both sports, she was a Michigan Athlete of the Year and named High School Athlete of the Year by The Jewish News and the Michigan Jewish Sports Foundation.