Complex sentence: She corresponded with queen Catherine de' Medici of France, and during her nine years of regency (1574--1583), her politics were so pro-Venetian that she became hated by the Republic of Genoa.
Split into simpler sentences: She corresponded with queen Catherine de' Medici of France. During her nine years of regency (1574--1583), her politics were so pro-Venetian that she became hated by the Republic of Genoa.