Hirner, who competes for SC Erzbergland, made her international debut on 7 January 2017 at the Youth Cup competition in Harrachov, Czech Republic, where she finished third place on the middle hill and over 4 kilometers behind Gyda Westvold Hansen and Jenny Nowak.

With these successes behind her, Hirner competed in the 2018 Nordic Combined Grand Prix, which was held for the first time for women, on 18 August 2018, and achieved fourth place in both competitions using the Gundersen method.

[1] In the team competition for special ski jumpers, however, she managed to make it onto the podium in third place together with Marita Kramer, Claudia Purker and Lisa Eder.

[4][5] At the 2020 Winter Youth Olympics in Prémanon, Hirner won the gold medal both in the individual event ahead of Ayane Miyazaki and with the mixed team.

She also achieved this at the 2020 Nordic Junior World Ski Championships in Oberwiesenthal in the Gundersen individual behind Jenny Nowak and Gyda Westvold Hansen.

In the first mixed team competition, however, she narrowly missed out on a medal, finishing fourth together with Johannes Lamparter, Sigrun Kleinrath and Manuel Einkemmer.

At the end of the season in Nizhny Tagil, Hirner was on the podium on both days of the competition and ultimately finished the Continental Cup in seventh place in the overall ranking.

After the ski jumping, which Hirner finished seventh, more than a minute behind the leader Gyda Westvold Hansen, a title win was already out of the question, but the medal ranks were certainly within reach.