The New 52 universe does not have a "Diana Prince" identity as stated in an interview by series writer Brian Azzarello. However, when she and Superman began dating, for her civilian identity she used the Diana Prince alias whenever she was around Clark Kent; such as when she introduced herself to Lois Lane at Lois's housewarming party under that name.
Artemis of Bana-Mighdall briefly served as Wonder Woman during Hippolyta's trials for a new Wonder Woman. Orana, a character similar to Artemis, defeated Diana in a new contest and became Wonder Woman in pre-Crisis on Infinite Earths continuity. Orana was killed during her first mission. Others who have donned the Wonder Woman persona include Nubia, Cassandra Sandsmark, and Donna Troy.
Diana sees Sir Patrick Morgan in the base, who reveals himself to be the true Ares, and tells her of his plan for a world without humanity by having them destroy each other. Ares proposes that Diana help him accomplish his vision of paradise, but Diana promptly refuses, not wanting to kill billions of innocents. Ares then reluctantly engages her in an epic battle while Steve and his comrades attempt to dismantle the plane harboring the mustard gas.