In January 1940 Heemskerk married FIDE Master Willem Koomen who worked for the Dutch Central Bank and gave birth to a daughter, who was also a player of note, but the marriage broke up in 1944.
Heemskerk grew up in Amsterdam, where her parents had a flower shop. Her father was an avid billiard and chess player. As a child she loved soccer and playing outside and at the age of eleven came down with the flu. During her recovery her father taught her to play chess.
When a hometown player named Max Euwe won the world championship in 1935 she was really bitten by the chess bug and only a year later both Fenny, who finished second, and her mother participated in the Amsterdam ladies championship. Two years later she won both the Amsterdam and Dutch women's championship when she defeated Catherine Roodzant who recaptured the title in 1938. In 1939 Heemskerk defeated her in the return match and until 1960 theses two ladies would dominate Dutch women's chess. To earn a living, she and her parents had begun running a shop where they did sewing and later sold curtains and drapes.
Heemskerk took part in the first world championship for women after the war in 1949/50 in Moscow. The title was vacant because Vera Menchick had been killed in 1944 during a London bombing. She finished in eighth place. Lyudmila Rudenko was the winner.
In 1951 she won the zonal tournament in Venice, which qualified her for the candidates tournament in Moscow in 1952. In Moscow when one of the Russian participants became ill her game with Heemskerk was postponed, but then Heemskerk herself got sick. Russian officials wanted her to play from a hospital but she refused and won the postponed game. Although she played very well, she had problems against some of the lower rated players and ended up tying for second and third behind Elizabeta Bykova. After that, her results began to fall off and she finished in ninth place in the Candidates Tournament at Moscow 1955 and only tied for 15–16th in the Candidates Tournament at Vrnjacka Banja 1961. Despite her lowly finish she did manage to defeat the third place finisher.
|With her daughter in 1951|
In 1968 the Chess Society of Amersfoort appointed her an honorary member and named the Fenny Heemskerk Women's Tournament after her. A WIM since 1950, FIDE awarded her the WGM title in 1977. In 1985 she was made a Knight in the Order of Orange Nassau.
In 1970 it was found that Heemskerk was manic depressive and suffering from delusions. She refused to learn anything about her illness and refused to take her medications. As a result, during one manic episode, she left to play chess in Mongolia without informing anyone.
Regularly a patient in psychiatric institutions, by the late sixties she had to give up her business and began receiving State benefits though she was able to work as a chess instructor for adult education classes, give chess lessons in schools, rehabilitation centers and in women's chess. Heemskerk was treated with great respect because of her performances and was guest of honor at many chess events.
Even at the age of 80 she played at the local chess club, but when she decided to stop all her medication her condition worsened and she died in a nursing home in Amersfoort on June 8, 2007 at the age of 87.
Heemskerk's opponent in this game was Ingrid Larsen (July 1, 1909 - February 25, 1990, 80 years old) was a Danish WIM (no relation to Bent Larsen) who was a challenger for the Women's World Championship in 1937, 1939 and 1949-50. She also won the Danish Women's National Championship title 17 times.
The game looks pretty calm on the surface, but the engines disclosed some really wild complications which the players avoided. That's understandable because it would not have been possible to calculate such deeply hidden and complex variations over the board. Heemskerk's finish was very nice.