Reintje de Leeuw was unmarried and born in 1917 in the municipality of Nieuwer Amstel as daughter of Hartog de Leeuw and Cato Bloemhof. She lived at home with her parents who, from 1935, lived at Brinkstraat 38 in Betondorp, a district in Amsterdam-East. Reintje however moved on 25 October 1940 to the family of her oldest sister Eva van Gelder de Leeuw on Voltaplein 30 parterre. She was deported on 24 February 1943 to concentration camp Vuhgt, where she stayed until her deportation from Vught to Auschwitz on 15 November 1943, a transport of in total of 1149 deportees.
On arrival in Auschwitz, ±18 November 1943, Reintje most likely was employed as a forced labourer. It is not known of her exactly, on which date and where she lost her life. Reason why after the war the Dutch Ministery of Justice ordered the municipality of Amsterdam to prepare a death certificate for Reintje de Leeuw, in which it was established that she lost her life in Auschwitz on 31 January 1944.
Sources include Amsterdam City Archives, archive cards of Hartog de Leeuw and Reintje de Leeuw, the Wikipedia list of Jew Transports from the Netherlands and the file cabinet of the Jewisch Council, registration card of Reintje de Leeuw.