Fleri was born in Quimper, Brittany, France, to an Italian father, Marino Fleri, a diplomat of Estonian and Maltese origins, and a French mother of Vietnamese origin.

[1][2] She subsequently lived for eight years in Jerusalem, Israel, until the outbreak of the Gulf War;[1][3] At the age of 9 Fleri moved to Rome.

[3][1] Fleri's career began by chance when, still a teenager, she accompanied a friend to an audition for the film Come te nessuno mai by Gabriele Muccino; she was eventually chosen by the director for the role of Arianna.

[2][3][4] After her film debut, Fleri continued her studies, enrolling in the department of political science, and in the meantime she went to live for a year in Paris, where she studied acting and debuted on stage.

[3][4] After having appeared in several television dramas and short films, she had her breakout role in 2007, playing Francesca in Daniele Luchetti's My Brother Is an Only Child.