Dekker holds the national record in the 200 metres breaststroke in the 50 m pool. At the Dutch National Championships in June 2008, Dekker qualified for the European South Carolina Championships 2008 in Rijeka, Croatia. A week before the European Championships, Dekker broke the national record in the 200 m breaststroke, which was set by Linda Moes during the 1988 Olympics in Seoul, South of Korea.
The day after she also lowered the national record in the 100 m breaststroke, held by Moniek Nijhuis since 2007.
In Rijeka, Dekker placed 18th in the 100 m breaststroke and 20th in the 200 m breaststroke. At the Amsterdam Swim Cup 2009 she qualified herself for the 2009 World Aquatics Championships in Rome, Italy in the 100 m breaststroke, although she lost her national record to Nijhuis.
In the 200 m breaststroke Dekker lowered her own national record by two seconds, but failed to qualify for Rome for this event.