[1][2] Born in Utrecht, Köster made her One Day International (ODI) debut at the age of 20, playing two matches in the 1995 edition of the European Championship, hosted in Ireland.
[4] Köster remained a fixture in the Dutch team throughout the rest of the decade, and began to be used higher in the order, including on several occasions as an opening batter.
[3] During the Dutch tour of Sri Lanka in March 1999, she scored what was to be her only ODI half-century, making 58* from 89 balls coming in fifth in the batting order.
[7] Outside of the European Championship, Köster's next international tournament for the Netherlands was the 2003 IWCC Trophy, the qualifier for the 2005 World Cup.
[3][13] She finished her career with 46 ODI appearances, behind only Pauline te Beest for the Netherlands, although that mark has since been equalled by Helmien Rambaldo and beaten by Carolien Salomons.