Trying to determine her ancestry was impossible without the auction notes. First, is this Münster in Nordrhein-Westfalen or is it Munster in southern Ireland? German and British aristocrats married frequently in this first era of globalization that crashed in 1914, partly because those nasty loose ends such as the needs and aspirations of ordinary subjects and citizens were ignored. I rambled around thepeerage and Wikipedia to no avail. However the auction catalog has a note that Google language tools translates as, "Marie Countess of Munster with dog Dandy. In 1890. Oil on canvas. Signed and dated lower right: Hente in 1890. Inscribed on the back: Countess Marie of Münster. Born 1 Juli 1848. Your dog Dandy was the favorite dog of the Emperor Frederick III of Prussia (1831 - 1888)... The countess always lived with her father, the ambassador Count Georg zu Münster and ran his house in London and Paris."