[1][2] In 1984, in Katowice she participated in European Girls' Junior Chess Championship and ranked in 7th place.
[3] In 1985, in Dobrna she participated in World Girls' Junior Chess Championship and ranked in 12th place.
She competed many times in the individual finals of the Dutch Women's Chess Championship and three times won this tournament: 1985 (shared 1st place with Hanneke van Parreren), 1987 and 1988.
[7] Harmsen thrice participated in Women's World Chess Championship West European Subzonal tournaments: Harmsen played for the Netherlands in the Women's Chess Olympiad:[11] Harmsen achieved the highest rating in her career on 1 July 1989, with a score of 2245 points, she was then ranked first among Dutch female chess players.
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