Complex sentence: She sought to inspire Titian by sending him a 1511 portrait painted by Giovanni Francesco Zaninello which showed her as a young woman and highlighted her girlish beauty, and was in turn based on an even earlier portrait.
Split into simpler sentences: She sought to influence Titian by sending him a 1511 portrait painted by Giovanni Francesco Zaninello which showed her as a young woman and highlighted her girlish beauty. This work was in turn based on an even earlier portrait.