English, Spanish, and DBpedia sources record Loredana Marcello's death in Venice on 12 December 1572, while she was still Dogaressa.
According to the English and Spanish Wikipedia entries, as well as the DBpedia structured data record, Loredana Marcello died in Venice on 12 December 1572, while still holding the ceremonial title of Dogaressa through her marriage to Doge Alvise I Mocenigo.
Her death came roughly two and a half years after her husband's election as Doge on 15 May 1570, a tenure that spanned one of the most consequential periods in sixteenth-century Venetian history, including the loss of Cyprus to the Ottoman Empire and the celebrated Christian naval victory at the Battle of Lepanto in October 1571. As Dogaressa, Loredana had represented the dignity of the Venetian state in ceremonial and charitable capacities throughout this period of war and diplomatic realignment.
Following her death, Alvise I Mocenigo continued to serve as Doge until his own death in 1577, having outlived his consort by roughly five years. Loredana's passing is noted in multiple modern biographical compilations, though as with much of her documented life, primary Venetian archival sources remain difficult to access directly, and secondary literature sometimes attributes to her a role in compiling remedies used during the subsequent 1575 Venice plague outbreak, though this claim lacks precise dating and is treated cautiously by historians.