At the beginning of 2012, Sundling won a silver medal in the sprint at the Winter Youth Olympic Games in Innsbruck and with the Swedish relay at the Nordic Junior World Ski Championships in Erzurum . In December 2012 she started in Sjusjøen for the first time in the Scandinavian Cup and achieved two top 10 results with ninth place in the 10 km freestyle and sixth place in the sprint. In January 2013 Sundling was junior relay world champion with the Swedish team in Liberec . On January 4, 2014 she achieved her first podium finish in the Scandinavian Cup with third place in the sprint in Skellefteå and won world championship titles in both sprint and relay at the subsequent Junior World Championships in Val di Fiemme . On February 15, 2015 Sundling made her debut in the cross-country skiing world cup over 10 km freestyle in Östersund and finished the race in 53rd place; Later in the month you get two more podium finishes at the Scandinavian Cup in Jõulumäe with second place each in the sprint in classical technique and two more podium finishes in the freestyle sprint. In the following month she got her first World Cup points in Lahti with seventh place in the sprint. At the end of the season she was tenth in the Scandinavian Cup overall standings. In the 2015/16 season she made it into the points twice in the World Cup. Her best placement was eighth in the sprint in Davos . At the U23 World Ski Championships in 2016 in Râşnov , she won the gold medal in the sprint. In March 2016 she won the mini tour in Otepää in the Scandinavian Cup and finally took third place in the overall ranking of the Scandinavian Cup. After finishing 16th in the World Cup mini-tour in Lillehammer at the start of the 2016/17 season, she became the Swedish sprint champion at the beginning of February 2017, as in the previous year. In the 2017/18 season she achieved five top ten finishes in the Scandinavian Cup, including second places in the sprint in Piteå and Trondheim, third place in the overall standings. At the World Cup finals in Falun , she finished ninth and came second in the sprint stage.
At the beginning of the 2018/19 season, Sundling won her first World Cup victory in the Lillehammer Triple, which she finished in 14th place. In January 2019 she achieved third place in the sprint in Dresden and, together with Ida Ingemarsdotter, second place in the team sprint and in Ulricehamn second place with the relay. At the season highlight, the Nordic World Ski Championships 2019 in Seefeld in Tyrol , she came fourth in the sprint. At the World Cup final in Québec , she finished sixth. She reached third place in the sprint stage and finally 17th place in the overall World Cup and ninth place in the Sprint World Cup. After finishing 17th in the Ruka Triple at the beginning of the 2019/20 season, she took her second World Cup victory in the sprint in Planica and also won second place in the team sprint there with Stina Nilsson . This was followed by third place in the sprint in Falun and 17th place in the ski tour. At the end of the season she won the sprint in Drammen and reached 11th place in the overall World Cup and second place in the Sprint World Cup.
Sweden
Planica
Drammen
Otepää