"Friederike of Mecklenburg-Strelitz", Johann Philipp Bach, circa 1795
So-called portrait of frederica of mecklenburg-strelitz (1778-1841), but it's probably the portrait of her sister duchess therese of mecklenburg-strelitz (1773-1839)
identification proposed by user ecummenic (talk) based on the comparison with some portraits of therese of mecklenburg (see images below) and the lack of physical resemblance of the sitter of this portrait to other representations of princess frederica. Date: circa 1795. Dimensions: height: 30.5 cm (12 in); width: 25.5 cm (10 in). Medium: pastel on vellum. Collection: Unidentified location. Bach - Friederike of Mecklenburg-Strelitz, pair