In 2018 and 2019, Berthelsen won the Greenland Football Championship with GSS Nuuk. In both years she was top scorer of the tournament.[4][5] She scored a hat trick in the 2018 finale at only 14 years old.[6]
In 2020, Berthelsen signed for Danish top flight side Fortuna Hjørring.[7][8][9][10] In the same year, she was named Greenland Sportsperson of the year by the Greenland Sports Association.[11]
In 2021, Berthelsen became the first Greenlandic player to appear in the UEFA Champions League, playing as a substitute against FC Barcelona in a round of 16 match.[12]
In 2022, she was loaned to Sundby in Denmark,[13] before coming back to Fortuna Hjørring in 2023.
International career
Berthelsen has 13 appearances for the Denmark U-19 team. She scored two goals against Turkey in October 2021.[14]