[1] Andexer took part in her first international races at the 2020 Biathlon Junior World Championships in Switzerland.

She only took part in the relay race there and finished in eighth place together with Kristina Oberthaler, Lisa Osl and Lara Wagner.

There, too, she finished second in the IBU Cup pursuit race in Martello and achieved a podium position for the first time.

[2][3] At the 2024 European Junior Biathlon Championships, she won the individual and the mass start, finishing third in the sprint behind her team-mate Lara Wagner and Sonja Leinamo from Finland.

The Austrian team with Oliver Lienbacher, Fabian Müllauer, Lara Wagner and Anna Andexer won bronze.