At the 2016 Belgian Championships, Vaelen swept the gold medals on every event and in the all-around in the Junior A-12 Division.[4] She then made her international debut at the 2016 Gymnova Cup and won the gold medal in the all-around in the Espoir division.[5]
At the 2017 WOGA Classic, Vaelen finished sixth in the all-around and placed eighth with the Belgian team.[6] She then competed at the Belgian Championships and won the bronze medal in the all-around.[7] Then at the 2017 Gymnova Cup, she won the silver medal in the all-around and on vault and balance beam, and she won the bronze medal on the floor exercise.[8] Her final meet of the 2017 season was the Top Gym Tournament where she placed eighth in the all-around and on vault, and she finished fifteenth on the uneven bars.[9]
2018
Vaelen returned to the WOGA Classic, this time placing twelfth in the all-around.[10] She then competed at the International GymSport and won the gold medal in the all-around.[11] Then at the Belgian Championships, she won the bronze medal in the all-around behind Fien Enghels and Margaux Daveloose.[12] She competed as a guest at the Dutch Championships and won the gold medal in the all-around.[13] She then competed at the Heerenveen Friendly where the Belgian team finished second behind the Netherlands, and Vaelen placed fifth in the all-around.[14] In August, she withdrew from the Junior European Championships due to a leg injury.[1] She returned to competition in November at the Gymnova Cup and won the gold medal in the all-around.[15] Her final meet of the season was the Top Gym Tournament where she won the gold medal in the all-around.[16]
2019
Vaelen once again began her season at the WOGA Classic, and she finished sixth in the all-around.[17] Her next competition was the City of Jesolo Trophy where the Belgian team won the bronze medal behind Russia and the United States, and she finished nineteenth in the all-around.[18] She then won the gold medal in the all-around at the International GymSport.[19] At the Belgian Championships, she won the bronze medal in the all-around.[20] She then competed at the FIT Challenge and helped Belgium win the team gold medal.[21]
Vaelen made her senior debut at the 2020 L'International Gymnix in Montreal where she helped the Belgian team win the silver medal behind the United States.[23] However, this was her only competition of the season due to the COVID-19 pandemic.
In August, Vaelen competed at the European Championships in Munich, where she contributed to Belgium's fifth-place finish in the team final. Individually, she placed fifth in the all-around, and finished fourth in the vault final behind Zsófia Kovács, Asia D'Amato and Aline Friess with a total score of 13.583.[27]