Through her work at the Weimarer Hoftheater and in concerts throughout Europe, she was a highly esteemed Kammersängerin and achieved great popularity during her lifetime.

[2] In 1866, Agnes and her family left Winsen and moved to Bremerhaven, and only a short time later on to Heppens [de], now part of Wilhelmshaven, where her father founded a hotel.

[9] From 1884, she was able, thanks to an anonymous patron, to study for the stage Richard Wagner's niece, Johanna Jachmann-Wagner who had appeared as Elisabeth in the world premiere of his Tannhäuser.

[17][18] The Munich Allgemeine Zeitung praised Stavenhagen's "exceedingly beautiful sounding and musically confident soprano" on 22 October 1900[19] and the Münchner Neueste Nachrichten of 23 October 1900 noted how "her bright, sympathetic soprano literally hovered above the choir's harmonies, which were sung in extreme calm".

Their Lieder- und Duettenabende were popular, in which Agnes performed with the contralto Iduna Walter-Choinanus and pianist Hermann Zilcher, among others.

[21] The Stavenhagen couple were friends with Heinrich VII, Prince Reuss of Köstritz and his wife, the Weimar Princess Marie Alexandrine of Saxe-Weimar-Eisenach, who generously supported their art.

During this time, she cultivated a friendship with the piano manufacturer Edwin Bechstein and his wife Helene and had access to their salon, a meeting place for artists, industrialists and politicians of the Berlin society.

Back in Kirschau, she suffered a severe stroke in the summer of 1945 and was subsequently placed in a diaconal nursing home in Bautzen, where she died on 30 September 1945 at the age of 85.