She studied at the UdK Berlin with Prof. Robert Gambill and at the HMT Leipzig with Prof. Regina Werner-Dietrich as well as with Margreet Honig and Renata Scotto. In 2010 she won the Competizione dell'Opera in Dresden and received second prize at the Concours Suisse Ernst Haefliger in Gstaad/Bern.

2012 Mandy Fredrich celebrated her Salzburg Festival debut by performing the Queen of the Night Die Zauberflöte under the baton of Nikolaus Harnoncourt which marked her international breakthrough. She also sang that role at the State Operas in Munich, Berlin and Hamburg, the PdlA Valencia and at the Grand Théâtre de Genève.

Other engagements included Amaltea Mosé in Egitto conducted by Enrice Mazzola and directed by Lotte de Beer and Antonia and Giulietta The Tales of Hoffmann in the spectacular new production by Stefan Herheim at the Bregenz Festival, Primadonna Viva la mamma at the Zurich Opera House, Micaëla Carmen at the Gewandhaus Leipzig, Contessa Le Nozze di Figaro at the Deutsche Oper Berlin and the NNT Tokyo, Donna Anna Don Giovanni at the Semperoper Dresden, the Hamburg State Opera and the Cologne Opera House, Hüter der Schwelle Die Frau ohne Schatten at the Teatro alla Scala in Milan and Marzelline Fidelio at the Berlin State Opera.

In the seasons 2015/16-2017/18 the soprano was a member of the ensemble at the Staatsoper Stuttgart and was celebrated as Marguerite Faust in Frank Castorf's highly successful production, as Contessa Le Nozze di Figaro, as Donna Anna Don Giovanni, as Fiordiligi Cosi fan tutte, as Micaëla Carmen, as Antonia The Tales of Hoffmann, as Iphigénie Iphigénie en Aulide and most recently as Agathe Der Freischütz.

Mandy Fredrich can also be seen regularly on the concert stage. She has been invited, for example, to sing Mendelssohn's Lobgesang and Elijah, Mozart's Requiem and Brahms' Requiem, Beethoven's 9th Symphony, M. Weinberg's 21st Symphony ("Kaddish") and a selection of Strauss' Orchestral Songs. Her Lied recital "You will not cry - songs from the beginning and end of love" was received with great enthusiasm at the Potsdam Easter Festival and in the State Gallery in Stuttgart.

Recent engagements included her role debut as Frau Fluth The Merry Wives of Windsor conducted by Daniel Barenboim at the Berlin State Opera; gala concerts at the Teatro alla Scala in Milan conducted by Manfred Honeck and her house debuts at the Vienna State Opera and at the Royal Opera House London as Marguerite Faust conducted by Frédéric Chaslin and Dan Ettinger.

Unfortunately, her house debuts in Lyon as Contessa and Agathe, in Naples and Florence as Donna Anna, as well as further engagements as Marguerite at the Staatsoper Stuttgart and as Frau Fluth at the Berlin State Opera were cancelled due to the pandemic.

However she got the opportunity to sing her song recital in the Nikolaisaal Potsdam, to perform once again the Queen of the Night Die Zauberflöte at the Berlin State Opera and to make her debut in Beethoven's 9th Symphony at the Festival di Maggio Musicale Fiorentino conducted by Zubin Mehta. ​