She was born in Vienna as the eleventh child of Johann Michael Auernhammer and Elisabeth Timmer. Josepha Barbara Auernhammer studied with Georg Friedrich Richter, Leopold Anton Kozeluch and from 1781 Mozart, with whom she fell in love. On 27 June 1781, Mozart wrote of her: "Almost every day after dinner I am at H: v: Auernhammer's - The Miss is a monster! - plays delightfully though, however, she lacks the genuine fine and lilting quality of cantabile; she plucks too much." That year, Mozart dedicated his Violin Sonatas K. 296 and K. 376–80 to her.
Auernhammer corrected the printing of several sonatas by Mozart, and her piano playing together with Mozart was described enthusiastically by Abbé Stadler. During a house concert in Vienna Passauerhof on 23 November 1781, she played Mozart's Sonata for Two Pianos K. 448 and the Double Concerto K. 365. Further joint concert appearances took place in January 1782 and on 26 May 1782.
After the death of her father, Mozart conveyed a housing at Countess Waldstätten's to Auernhammer which was located in the Leopoldstadt district of Vienna. In 1786, she married Johann Bessenig (c. 1752 – 1837), with whom she had four children. She regularly participated in concerts in private venues and at the Burgtheater. Already on 25 March 1801, immediately after the work was finished, she played the Piano Concerto in C major, Op 15 by Ludwig van Beethoven.
Her last public concert was on 21 March 1813 together with her daughter Marianna Auenheim who was a known voice teacher and pianist. Auernhammer wrote predominantly piano music, and especially variations which are characterized by extensive knowledge of pianistic techniques and artful use of the instrument.
She died in Vienna and was buried in St. Marx Cemetery.
- Michael Lorenz, "New and Old Documents Concerning Mozart's Pupils Barbara Ployer and Josepha Auernhammer", Eighteenth-Century Music, Vol. 3 (2006), No. 2, S. 311–322