As the wife of the foreign minister she made her salon at Tauentzienstraße 12a a meeting place of diplomats.

In 1903 she married Gustav Stresemann (1878–1929), who later became Chancellor and Foreign Minister of the Weimar Republic, and bore him two sons, Wolfgang (1904–1998) and Hans-Joachim (1908–1999).

Her brother, Kurt von Kleefeld, was the last person in Germany to be ennobled, when he was raised to the hereditary nobility of the Principality of Lippe by Leopold IV, Prince of Lippe "in recognition of his loyal service" to his noble lord, Christian Kraft of Hohenlohe-Ohringen, Duke of Ujest, on request by the latter, on 12 November 1918, the same day as the Prince's abdication.

[1] Kleefeld is mentioned in one of the fictitious quotes the 8 November 1926 issue of Time satirically attributed to quite a number of prominent people under the headline: Had they been interviewed, some people who figured in last week's news might have related certain of their doings as follows: Gustav Stresemann, Foreign Minister of Germany: "A story went the rounds of Berlin last week that my ability to entertain lavishly on a salary of $6,400 a year is due to the kindly furtherance of my affairs by the multimillionaire Dr. von Kleefeld, my bachelor brother-in-law.

"[2] In August 1929, when Käte Stresemann hosted the program for spouses at the 25th World Advertising Congress in Berlin, Time described her as "no hausfrau, but a young, elegant, cosmopolite, English speaking Jewess, a woman equipped with the conversation of the polite world, equal to parlor or nightclub."