Because she continued to support and propagate the ideals of Nazism after World War II and the death of her husband, she became known in the Netherlands as the "Black Widow".

A year later she made a trip with Wim to the Dutch East Indies, where her eldest brother Dolf worked as agricultural engineer.

[2] The youngest son was born on 28 April 1945 in Terschelling on the day her brother Wim Heubel fell in battle fighting with SS forces near Elst.

[citation needed] Immediately after the war, Meinoud Rost van Tonningen died in the Scheveningen prison while awaiting trial.

The motive would have been that her husband, as President of De Nederlandsche Bank, knew too much about illegal money transactions by prominent people.

The former RIOD (National Institute of War Documentation) employee, A. J. van der Leeuw, supported her version during the television show Het zwarte schaap (The Black Sheep) and suggested that her husband may have been driven to commit suicide in prison.

[citation needed] In her book, In Search Of My Wedding Ring, Rost van Tonningen-Heubel accused Prince Bernhard of bearing the main responsibility for her husband's death, as he had been head of the Domestic Forces, claiming that her private archive contained evidence of this.

Her supervisor, Clerk of the Senate Anton Leo de Block, put her three sons under the guardianship of her brother-in-law Nico Rost van Tonningen, who was in the service of Queen Juliana.

She maintained lifelong contacts with many prominent ex-Nazis and Nazi sympathizers, such as the French professor Robert Faurisson; David Irving; Artur Axmann; Gudrun Himmler (daughter of Heinrich Himmler); Ilse Pröhl (widow of Rudolf Hess); Gertrud and Arthur Seyss-Inquart; Erich Priebke; Miguel Serrano; Matt Koehl, commander of The New Order; Thies Christophersen; Léon Degrelle; Princess Marie Adelheid of Lippe-Biesterfeld; Paula Hitler; Richard Edmonds; Hanns Albin Rauter; Franz von Papen; Hjalmar Schacht; Ernst Zündel; General Otto Ernst Remer; Manfred Roeder; Colin Jordan; Udo Walendy; Horst Mahler; Alfred Vierling; members of the Vlaams Blok; and many others.

Until her death in 2007, Rost van Tonningen-Heubel received a modest widow's pension from the Dutch state, as her husband had once been a member of parliament.

One of her sons, Egbert (Ebbe) Rost van Tonningen, published a memoir in 2012 about his childhood, In Niemandsland ("In no man's land").