Vienna Wolfe by Mary Lancaster

Vienna, 1814: Europe makes a historic peace…and dances.

Colonel Francis Wolfe, military hero and the new Earl of Warenton, is prepared to do his duty and marry well. He has almost decided upon the well bred and beautiful Miss Sylvia Renleigh, without ever noticing the quiet young woman who is her aunt’s over-worked companion. Until Elise practically walks under the hooves of his stallion. It never enters his head that she was daydreaming of him.
Impoverished emigrée, Elise de Sancerre, knows that the earl would never normally look at her. Yet when they meet again at a masked ball, where the world expects him to propose to Sylvia, everything changes. Throw a managing sister and a missing tiara into the equation and all bets are suddenly off.