On 11 April 1860 she married Eugène Arnould Henri Charles François Marie, comte de Mercy-Argenteau (22 August 1838 – 2 May 1888).

After his defeat at the Battle of Sedan, she visited him for a last time when he was a prisoner of the Prussians at Schloss Wilhelmshöhe and consoled him playing music.

Her advocacy of music by The Mighty Handful favored that of César Cui and facilitated the production of the latter's opera Prisoner of the Caucasus in Liège in 1886.

Cui's collection of piano pieces entitled À Argenteau is a musical reminiscence of the count and countess' estate in Belgium.

La Comtesse de Mercy-Argenteau died of cancer on 8 November 1890 in Saint Petersburg, Russia.