Amundsen, who starts for the Asker Skiklubb , took part in junior races until 2018. At the Nordic Junior World Ski Championships in Goms in 2018 , she took 11th place over 5 km classic, ninth place in the skiathlon and seventh place with the relay. She ran her first races in the Scandinavian Cup at the beginning of the 2018/19 season in December 2018 in Östersund , which she finished in 17th place in the sprint and tenth place over 10 km freestyle. In the same month she completed her first race in the World Cup in Beitostølen and achieved 39th place over 15 km freestyle. In the further course of the season she reached 12th place in the overall ranking of the Scandinavian Cup with three top ten placements. In March 2019, she took her first World Cup points in Oslo with 18th place in the 30 km mass start race. The following year she won the gold medal with the relay at the U23 World Championships in Oberwiesenthal . In addition, she was there ninth over 10 km classic and seventh in the 15 km mass start race.