As a junior Cornelissen won three national Dutch titles; twice with Ayesha and once with Mr. Pride. In 2004 she won her first senior title at national level when she won the Z2-class with Parzival. That same year she became national champion in the Reserve Championships in the ZZ-light-class with, followed by the same title in the ZZ-heavy-class title in 2005, both times on Parzival. In 2007 she and Parzival became Dutch national champion in the heavy-class and she won two silver medals at International Grand Prix meetings in Falsterbo and Herentals. In Falsterbo she finished second in the Grand Prix Spécial, while in she won the GPS in Herentals. During the Grand Prix in Rotterdam she and her team mates won the gold medal in the Nations competition, she became third in the Grand Prix Spécial. She won another GPS bronze medal in Arnhem.
In 2008 she became the champion in the Reserve Championships again, this time in the ZZ-heavy-class. She also became national champion at the Dutch Championships that year. Cornelissen and Parzival went on to win the International Grand Prix of Indoor Brabant, while they became second in the Grand Prix Spécial. At the Grand Prix meeting in Aachen they became second in both the Grand Prix as well as the GPS.