On 31 October 1956, following the revival of the Hungarian Social Democratic Party during the Revolution, she became president of the Party. On 1 November she attended the Socialist International Meeting in Vienna, Austria. The following day, 2 November The Hungarian Government appointed her a delegate to the United Nations General Assembly. On 3 November her Party nominated Kéthly for a ministerial position in the new coalition government of Imre Nagy but at dawn the following day, 4 November 1956, the Soviet Union invaded Hungary and she was advised to fly to New York City and appeal to the U.N. General Assembly on behalf of Hungary. Eventually she settled in London, United Kingdom, where she carried on writing and editing Socialist publications. In 1962 the Hungarian Supreme Court reviewed Kéthly's 1954 pardon and, "in absentia", imposed on her a three-year prison sentence for anti-state activities.