In 1945, Margarete and Gudrun left Gmund as Allied troops advanced into the area. After the invasion of Bolzano, Italy, by the U.S. Army in May 1945, Margarete and Gudrun were arrested. They were held in various internment camps in Italy, France, and Germany. During her internment, Margarete was interrogated, but it became clear that she was not informed of the official business of her husband, and was described as having a "small-town mentality" which persisted throughout her questioning. In September 1945, Margarete Himmler was again interrogated, but this time it was during the Nuremberg trials. Margarete and Gudrun were then detained at the Flak-Kaserne Ludwigsburg internment camp. Since they were not accused, she and Gudrun were released in November 1946 from internment. They took refuge for a time with the Bethel Institution of Bielefeld. Margarete's stay there was expressly endorsed by the Executive Board of the Bethel Institution, but this was not without controversy. On 4 June 1947, in the European edition of the "New-York Tribune", an article appeared entitled, "Widow of Heinrich Himmler Lives Like a Gentlewoman". Margarete was categorized in 1948 at Bielefeld as a lesser offender (Category III) and was to be denazified accordingly. In 1950, Margarete retained a lawyer to challenge this classification, since she claimed that her early Nazi Party membership was no more than "nominal" and that her high rank resulted from her early service with the German Red Cross, in which she had served since 1914. Margarete maintained that while she had been the wife of the "Reichsführer-SS", she remained far from the spotlight. Nevertheless, the denazification committee in Detmold revised her classification, and contended that she likely supported the goals of the Nazi Party and endorsed the actions of her husband. Her lawyer insisted during the follow-on appeals process that Margarete could not be held responsible for the actions of her husband, and countered that the official decision was guided by the idea of "Sippenhaft", which meant she was responsible by familial connections. On 19 March 1951, she was finally classified as "Mitläufer" (Category IV). According to this judgment, she was not to be held accountable for the crimes of her husband, despite that she had not been distant from them.