Thanks! What about Hendrik Bock?
And have you managed to read the name of the witness at her aunt's marriage to Johann Caspar Fizer?
According to Merck's book partially available on Google Books, Frau Hofmann (Marie Antoinette nee Ravanel) had three nieces: one niece, C. Reynier (or Reigner), in Lausanne. She was the daughter of Marie's sister Mme Chapuis (Sara Louise nee Ravanel). Caroline Christiane Henriette Chapuis married Jacques François Reynier, who died in 1773, (death mentioned in the book as 'had already died in 1774').
The second niece was a governess in Homburg "Mlle Rabennel". She could be Eugenie, but...
The third niece who was single and living in Holland is more likely to be Eugenie. But Eugenie or Caroline Victoire Ravanel was still called Ravanel and not Mme Rinsby in 1786 when her aunt died (the 11 Oct 1786 deed) and she left Beverwijk and went to Trévoux with Wolff and Deken in March 1788, she would have had to marry and become a widow during this short period of time. One other option is that she had married and become a widow whilst living in Trévoux, which is even less likely. The last option is that she had invented her marriage and husband.
https://books.google.nl/books?id=aKo-0yKvAgcC&pg=RA3-PA315&dq=merck+ravanel&hl=nl&newbks=1&newbks_redir=0&sa=X&ved=2ahUKEwi_m-eBqdCNAxXjhv0HHUVIH_kQ6AF6BAgFEAM#v=onepage&q=Reignes&f=falseA Google (terrible) translation:
...d'Epreville marries. She was godmother to Adelheid Merck; see Letter 864, note 1. - Caroline, the eldest princess of Darmstadt, married to Friedrich von Hessen-Homburg since 1768, also wished, in 1777, to have Ravanel as governess for her children; see Jacobi, Goethe's Lila, p. 61. The Darmstadt Frag- und Ananzeigersblättgen No. 33, of August 17, 1778, also names Mademoiselle Rabenell, governess of Homburg, among the travelers who arrived. - Another niece, C. Reynier, in Lausanne, entrusted Merck with the administration of the estate of her aunt Fises on September 23, 1786, who had inherited an affair from her aunt Katharina ("the" Ravanel). cf. Letter 852. - Another
unmarried niece lived in Holland; cf. von d'Epreville, November 18, 1786.
Could they be confusing Caroline Victoire Ravanel (Eugenie) with Caroline Christiane Henriette Chapuis (C. Reynier)?