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. This was followed by further starts in the youth and junior categories. Andexer won her first race in December 2022 at the
IBU Junior Cup in
Martell. The following season, she won three races in a row at the IBU Junior Cup in
Ridnaun and was then allowed to compete in the
IBU Cup. There, too, she finished second in the
IBU Cup pursuit race in Martello and achieved a podium position for the first time. 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. Shortly afterwards, she only won a medal in the mixed relay at the
2024 Biathlon Junior World Championships. The Austrian team with Oliver Lienbacher, Fabian Müllauer, Lara Wagner and Anna Andexer won bronze. In the individual races, Andexer achieved a top 10 finish in every competition. ==Biathlon results==