In existographies, Minna Herzlieb (1765-1837) was the 18-year-old “foster daughter” of the printer and publisher Karl Frommann (1765-1837), whom German polymath Johann Goethe fell in love with in the winter of 1807 to 1808, and who it is said was the starting mold for the character of Ottilie of Goethe’s 1809 physical chemistry based novella Elective Affinities (see: Goethe timeline), who, like Minna, is adopted niece of Charlotte’s deceased best friend, and who, like Minna (who is dispatched away: “the marriage of her younger sister was seized as the occasion of getting her away from Jena, and the dangerous intimacy with Goethe”), is gotten rid of by sending her away to boarding school. [1]
Minna returned to Jenna as the betrothed wife of a young professor, whom however she did not marry. Not until 1821 did she become a wife—and, supposedly, a wretched one, according to Adolf Stahr, who first made public this strange story. [3]
Sonnets
The product the love affair was a cycle of seventeen sonnets written as a dual with Minna's other admirer, the romantic poet Zacharias Werner (1768-1823):

who seems to have been the character behind the architect character of the novella, who attempts to win the affections of Ottilie in competition with Eduard. [2] Sonnets occur in the novella as well. [1]
References
1. Goethe, Johann. (1903). J.W. von Goethe’s Works: Life of J.W. von Goethe, Volume Two (by George Henry Lewes, with ten Illustrations) (Elective Affinities, pgs. 318-27). London: John C. Nimmo.
2. (a) Goethe, Johann. (1971). Elective Affinities (translation and introduction by R.J. Hollingdale; chronology and further reading by David Deissner, 2005). Penguin.
(b) R.J. Hollingdale – Wikipedia.
(c) Carl Friedrich Ernst Frommann – Wikipedia.
(d) Zacharias Werner – Wikipedia.
3. Stahr, Adolf. (1870). “Goethe’s Frauengestalten” 3te Auflage, ii, 261 seq.