Born into the family that belonged to the Bohemian nobility, Sidonie Amálie Vilemína Karolína Julie Marie Nádherná of Borutín was the youngest child of landowner Karel Boromejský Jan Ludvík Baron Nádherný of Borutín (1849–1895), and his wife Baroness Amalie Klein von Wisenberg (1854–1910), youngest daughter of the Bohemian businessman of German origin Albert Baron Klein von Wisenberg (1808-1877).

She reconciled with Kraus in 1915, who wrote much of his drama The Last Days of Humanity at her residence, castle in Vrchotovy Janovice, but they separated again at the end of the war.

In 1920, Nádherná married the Austrian physician, Count Maximilian von Thun und Hohenstein (1887–1935) at Heiligenkreuz Abbey, but the relationship did not last.

Sidonie von Nádherná's correspondence with Rilke and Kraus, now published, reveals her significance as a discussion partner, "creative listener," and as a representative of late Habsburg culture.

In addition to Rilke and Kraus, her circle also included the architect Adolf Loos, the writer Karel Čapek, the composer Dora Pejačević, and the painter Max Švabinský.