Simeoni was born in Rome and initially studied classical linguistics, later followed by a degree in operatic studies at the Conservatory in Adria. She continued her studies with Raina Kabaivanska at the Accademia Chigiana in Siena and also studied at the Istituto Vecchi-Tonelli in Modena and the State University of Sofia. Simeoni performs regularly at La Fenice in Venice, where her roles include Adalgisa (»Norma«), Léonor (»La Favorite«), Azucena (»Il Trovatore«), Sélika (»L’Africaine«), Carmen and Eboli (»Don Carlo«), as well as at Zurich Opera, with roles such as Isoletta (»La straniera«), Sara (»Roberto Devereux«), Giovanna Seymour (»Anna Bolena«), Eboli (»Don Carlo«) and Amneris (»Aida»«). Other notable appearances include Charlotte (»Werther«) for the Metropolitan Opera, New York, Teatro Massimo di Palermo, Teatro di São Carlos in Lisbon and Rome Opera, Marguerite (»La Damnation de Faust«) for Rome Opera, Adalgisa for Savonlinna Opera Festival, Teatro Real, Madrid, and in Cagliari, Sara for Deutsche Oper Berlin and Teatro Real, Preziosilla for London Royal Opera House and Dutch National Opera, Agave (»The Bassarids«) for Rome Opera, Hedwige (»Guillaume Tell«) for the Rossini Opera Festival in Pesaro, Carmen for Arena di Verona, Florence and for Teatro Regio, Turin, Amneris (»Aida«) in Macerata.
Simeoni’s concert repertory includes Verdi’s »Requiem« (including performances in Florence under Gatti, in Venice under Chung, in Bologna under Mariotti and in Bucharest under Luisi), »Messa per Rossini« at La Scala, Milan, under Chailly, and recitals including French songs by Berlioz, Debussy and Fauré, Wagner’s »Wesendonck Lieder« and Mahler’s »Des Knaben Wunderhorn«.