A close friend of Helena P. Blavatsky, Wachtmeister was born on March 28, 1838, in Florence, Italy. Her parents were the Marquis de Bourbel, formerly of the French diplomatic service, and Constance Bulkley. She lost her parents when she was very young and was sent to an aunt in England, where she lived and in 1863 married a cousin, Count Karl Wachtmeister, then Swedish and Norwegian minister at the Court of St. James. After three years, they moved to Scandinavia, where her husband served as a government minister in Copenhagen and Stockholm. Wachtmeister was widowed in 1871. She had one son, Count Axel Raoul, a well-known musical composer in his day.
Wachtmeister joined the Theosophical Society in 1881 and met H. P. Blavatsky in London in April 1884. She was secretary and treasurer of the Blavatsky Lodge in London and also worked for the Theosophical publishing company there, contributing generously to its funds. In 1887, Wachtmeister, the Keightleys, and Blavatsky acquired a large house at 17 Lansdowne Road, London, where Blavatsky continued to write The Secret Doctrine.
In March 1888, the President, Henry S. Olcott, who had just finished a strenuous Indian tour, decided to leave Adyar, the Theosophical headquarters near Madras (now Chennai), India, and recuperate at Ootacamund. He held a meeting of the Executive Council, which appointed Wachtmeister as an additional secretary to the Western Section of the TS. In 1891, Olcott formed a League of Theosophical Workers, of which Wachtmeister became the first president; later that year, after the death of Blavatsky, Wachtmeister traveled to Adyar, where Olcott appointed her as president of the Women' s Education League, which worked to further the education of Indian women.
Olcott had kept a diary covering the years since his first meeting with Blavatsky in America (1874). In 1893 he asked Wachtmeister to arrange for its publication. She wanted Olcott to delete passages that she considered derogatory to Blavatsky. Olcott did not agree, so he had the diary published as
Old Diary Leaves (London: Putnam, 1895). Late that year, Wachtmeister, Besant, and Bertrand Keightley rented a property on four acres of land at Benares (now Varanasi), which eventually became the headquarters of the Indian Section.
In February 1895, Olcott learned that William Q. Judge was considering secession from the Society; he left immediately for Calcutta to consult with Wachtmeister and Annie Besant regarding the best course of action. At the 1896 Adyar convention, Olcott paid glowing tribute to Wachtmeister in his presidential address, saying that she, "after performing prodigies of platform, social, and private work in Australasia, is now devoting herself enthusiastically to the helping of the American loyalists to reconstitute their Section." Annie Besant also went to America in March 1897 to help rebuild the Section, which had been devastated by the Judge secession. She was met in New York by Wachtmeister, who travelled with her on a long tour that included lectures in seventy cities. After a considerable period in America, in 1899 Wachtmeister did an extensive lecture tour of France and India, resulting in the formation of many new lodges.
Wachtmeister published an important account of her early association with Blavatsky as Reminiscences of H. P. Blavatsky and "The Secret Doctrine” (1893). She died on September 23, 1910.