Although Teodora abandoned her family name when she entered the Catholic Church, Venetian tax records indicated that she grew up in the Contanto family. Her parents owned a jewelry store, and Teodora was apprenticed to her mother as a shop girl. A visitor to the shop in 1462 wrote: "Bought a pair of diamond earrings today for Margarita, at the Contantos' shop around the corner. A charming young girl helped box them. When she handed me the earrings, our fingers touched. I had to leave the shop at once. Oh Lord, I wish I'd never married".
Court records indicate that by the time Teodora turned 17, she was doing far more than just touching. On 26 November 1467, she engaged in adultery with a married man, and his wife alerted the Venetian courts. As was common in these sorts of situations, her parents reacted by sending her to a nunnery to live the rest of her life in prayer and silence.
Teodora entered Santa Maria degli Angeli in 1467, determined to do penance for her crime. But, in 1473, she deserted the Church, leaving a statement nailed to the front door. In it, she wrote that life in the cloisters was sterile and "earthly", and that only in "partnership with another" could one "truly enter the arms of God". Teodora opened La Rosa della Virtù the same year. According to the poet Pietro Bembo, who was a frequent customer, her bordello was "the church for a new sect of Catholicism".
In 1485, she was introduced to the assassin Ezio Auditore da Firenze by the thief Antonio de Magianis, and Auditore proved his skills to her by killing a man who had murdered a few of her prostitutes. Contanto told Auditore that he could assassinate Emilio Barbarigo by winning a golden mask for Carnevale, and she supplied some of her courtesans to help Auditore with blending in with the crowd as Barbarigo prepared to give a speech from his boat. Auditore managed to evade capture by Barbarigo's searching guards, and he killed him with a shot from his hidden gun. In 1488, Contanto helped Auditore with stealing a Piece of Eden from Rodrigo Borgia, and she attended his initiation into the Hashshashin order, of which she was secretly a member. In 1499, Contanto and several other Assassins caused disturbances in Rome to distract Papal guards from the Sistine Chapel, where Auditore took the Papal Staff from Borgia, who was now the Pope.
Contanto would return to Venice to lead the courtesans, and her brothel was burned to the ground by a disgruntled bishop in 1516 after Contanto refused to allow for him to sleep with one of his courtesans for free. It is unknown what happened to her.