She studied at the Rijksakademie van beeldende kunsten (State Academy of Fine Arts) in Amsterdam.

[1] In 1932 Klaassen won a Prix de Rome for monumental and decorative sculpture.

[3] Klaassen's work was included in the 1939 exhibition and sale Onze Kunst van Heden (Our Art of Today) at the Rijksmuseum in Amsterdam.

[4] In 1949 Klaassen was chosen to create a monument in Arnhem honoring women in wartime.

She also exhibited with Sonsbeek and Sint Lucas [3] Klaassen died on 30 September 1989 in Heemstede.