Grosz was born into a Jewish family in Szilágysomlyó, then Austria-Hungary, today Șimleu Silvaniei, Romania. She studied piano at the Royal National Hungarian Academy of Music in Budapest with István Thomán. She gave her first concerts in 1897 Budapest and in 1898 and 1899 in Leipzig and Berlin with good success. From 1898 on she lived constantly in Berlin, where she studied with Teresa Carreño.
In 1911 she resigned from her concert career to marry Adolf Weissmann (1873-1929), a well known Berlin music critic and author of biographies of Bizet, Chopin, Verdi, and Puccini. After her retirement from the concert circuit, Gisella Grosz continued as a teacher of the piano. With her husband, she hosted frequent musicales in the 1920s, until his untimely death in 1929. She was listed in Berlin telephone directories from 1937 to 1940 as Gisella Weissmann (Weißmann). In 1940 the statutory Jewish middle name Sara was added to her listing, and in 1941 Jews were omitted altogether. In January 1942 she was deported to Riga, Latvia, and died there in that year.
Grosz and Weissmann had in 1908 a child born out of wedlock, Ilse. The daughter became a pianist too, taught mainly by her mother in Berlin and Konrad Wolff in Paris. From 1933 on Ilse Weissmann lived in France, England and Italy and finally emigrated to the US, where she died in 2000.
- Adolf Weißmann: Berlin als Musikstadt: Geschichte der Oper und des Konzerts von 1740 bis 1911. Berlin, Schuster & Loeffler, 1911
- Walter Niemann: Meister des Klaviers, Berlin, Schuster & Loeffler, 1919
- Országos Hirlap, 20 Dec 1897, p. 4; 21 Dec 1897, p. 8
- Musikalisches Wochenblatt, Leipzig, 28 Apr 1898, vol 38, no. 18, p. 266
- Országos Hirlap, 14 February 1898, p. 10
- Peter Muck: Einhundert Jahre Berliner Philharmonisches Orchester, Tutzing, Schneider, 1982
- Gerhard Dangel and Hans-W. Schmitz: Welte-Mignon Reproductions. Complete Library Of Recordings For The Welte-Mignon Reproducing Piano 1905-1932. Stuttgart 2006. ISBN 3-00-017110-X. p. 446