In 1973, she started studying law at the University of Utrecht and Amsterdam.
[5] In 1993 Valstein-Montnor started a RAIO-course (judge in training) together with four other candidates.
She graduated as the sole candidate, and in 1997 was appointed as the first female judge in Suriname.
[6] On 30 November 2007, the court-martial of the December murders commenced, and Valstein-Montnor was appointed presiding judge.
[8] On 1 January 2011 Valstein-Montnor was appointed acting president of the High Court of Justice of Suriname.