Thomsen was born in
Frederikshavn in 1998 and started playing golf when she was seven years old. At the age of 13, she was picked for the national team. By the time she accepted a golf scholarship to
Florida State University in 2018, she was one of the most accomplished junior golfers in the world, and at 17th spot in the
World Amateur Golf Rankings one of the top ranked players to ever sign for
Florida State University. Thomsen won the Danish Junior Matchplay Championship in 2011 and won her first international tournament in 2012, the Öijared Junior Open in Sweden. The next year, she appeared for Denmark in the
European Young Masters and the
European Girls' Team Championship. She appeared in the
European Ladies' Team Championship six times between 2014 and 2019. In 2015, when it was held at Helsingør Golf Club in her home country, she won the individual stroke play qualifying event. She carded rounds of 71 and 65 to finish a single shot ahead of England's
Alice Hewson and Finland's
Matilda Castren, and in the process jumped into a tie for second place on the European Ranking behind leader
Agathe Laisne. As a result, Thomsen played for Team Europe in the 2015
Junior Solheim Cup held at
Golf Club St. Leon-Rot in Germany. She also represented Europe in the
Patsy Hankins Trophy against Asia/Pacific twice, in 2016 and 2018. In 2018, she was the only returning European player from 2016, along with Bianca Fabrizio and
Frida Kinhult. At the 2015
World Junior Girls Championship in Canada, she won the team silver, along with Cecilie Bofill and
Line Toft Hansen. She finished in third place in the 2016
Portuguese International Ladies Amateur Championship, and third in the 2017
French International Lady Juniors Amateur Championship, where she shot a tournament personal best 3-under par 68 in the second round. She shot an all-tournament best 8-under par score of 64 in the final round to win the
French International Ladies Amateur Championship ahead of
Alessia Nobilio of Italy. She was runner-up in the European Nations Cup - Copa Sotogrande, in Spain. In 2017, Thomsen also played in the
Vagliano Trophy along with future fellow Seminole
Morgane Metraux, and competed in the
U.S. Women's Amateur. She finished in second place in the individual standings with a 12-under par total at the 2016 World Championships in Mexico, the
2016 Espirito Santo Trophy, and helped the Danish team with Marie Lund-Hansen and
Malene Krølbøll Hansen secure fourth place.
College Thomsen was one of five heralded recruits in head coach Amy Bond's best-ever recruiting class that arrived on the
Florida State University campus in September 2018, having turned down an offer from
Oklahoma State University. She was a big part of a star-studded group of freshmen in the
Florida State Seminoles women's golf team that included
Frida Kinhult, Caroline Hodge, Amelia Williamson and
Beatrice Wallin. With Thomsen in the lineup, Florida State tied the school-best for finishes in the ACC Championship (second) and the NCAA Auburn Regional Championship (second). By May 2020, she couldn't even walk, and decided to undergo the same operation as
Tiger Woods, a surgery designed to stabilize the lower part of her back. With the operation seemingly a success, following a year of rehabilitation, she competed in a small number of local tournaments in 2021. She completed her undergraduate degree at
Aalborg University in 2025. == Professional career==