A 2023 Thomas Guthrie opera titled for this singer features music originally written for members of this singer’s family. The names of this singer and a sister, Sophie (“so-FEE-eh”), were written above a sighing motif in a B-flat major piano sonata fragment. Music written for this singer includes an E-flat major “Christe Eleison” with a near-two octave jump on the final cadential chord and an F major “Et incarnatus est,” both in an incomplete C minor mass. This singer employed Maximilian (*) Stadler to manage her estate. This singer wrote a biography of her first husband with her second husband, Georg Nikolaus von Nissen. This woman’s husband wrote a symphony in four days in Linz on her first trip to her in-laws in Salzburg. (-5[1])For 10 points, name this woman who claimed she gave “scraps of paper” to Franz Xaver Süssmayr to complete the last work of her husband, Wolfgang Amadeus Mozart. ■END■ (10[1]0[2])