By establishing the date of death of Sophia van Leeuwen-Spanjar the official date is maintained as stated after the war by the Dutch Department of Justice.
The City of Wassenaar issued a certificate of death for Sophia van Leeuwen-Spanjar on the 18th of December 1945 which states that she died the 2nd of July 1945. This date seems likely.
Source: City of Wassenaar, certificate of death for Sophia …