Arndt debuted nationally in 2019, when she won silver at the German Championships, among gymnasts born in 2005, behind Sandy Kruse.[2]
In 2022 she took part in the qualifications for the European Championships, being 6th in the first and 5th in the second competition.[3][4] In June she was 7th in the All-Around, 5th with hoop, 7th with ball and 6th with ribbon at nationals.[5][6][7][8]
In March 2023 she competed at the Berlin Masters, being 4th in the gold category.[9][10] At the German Championships she was 6th overall, 5th with ball, 7th with hoop, 7th with clubs and 7th with ribbon.[11] In November she helped her club, Berliner TSC, win bronze in the club championships.[12][13]
In 2025 she was called up to join the national senior group, debuting at the Gymnastik International, winning gold in the All-Around and with 5 ribbons.[14][15] At the World Cup in Baku where Germany was 10th in the All-Around, 12th with 5 ribbon and 7th with 3 balls & 2 hoops.[16][17][18] A week later, in Tashkent, they took 4th place overall, 5th with 5 ribbons and 7th in the mixed event.[19][20][21] She was then selected for the European Championships in Tallinn, there the group was 10th in the All-Around and won an historical bronze medal, the first ever in the competition for a German group, with 3 balls & 2 hoops.[22][23][24][25]