Delforge started umpiring serious in 2008, and received her first international appointment in 2012. In 2016 Delforge won the Golden Whistle for best umpire of the year in Belgium. The same year she umpired in the Olympic field hockey tournament at the Olympic Games in Rio de Janeiro. She made history being the first Olympic debutant to also umpire the Olympic final. She also won the 2016 International Hockey Federation (FIH) Umpire of the Year award. During the 2018 Women World Cup in London, UK, Delforge umpired her 100th international game. She received the FIH 'Golden Whistle' for this achievement. She went on to umpire the final in that tournament.