Kraan is the oldest sibling in a family of 14 children. Initially she trained in handball, while working as a police officer, and changed to athletics only in 1954, aged 21. At her first major race in 1958 she improved the Dutch record in the 800 m to 2,16.6.
She shaved another 8 seconds from it the next year, and in 1960 qualified for the Olympics, where she was eliminated in a preliminary round.
After that she worked hard to improve her running technique and fitness, winning five national titles and setting nine national 800 m records between 1958 and 1963. During that period she also competed in 400 m, 440 yd and 880 yd races.
At the next Olympics in 1964 she was an obvious favourite, but finished in a mere seventh place.