Madame Nicolai
From superman.nu: Supermanica
The world-famous atomic scientist that the U.S. government invited to America in order to "experiment with atomic energyâ€. In order to be protected from spies, she takes on the alias of the “European glamor girl†Nikki Larue, who announces to the press that she has become Superman's fiancee as part of a ruse so that Superman “could guard [her] constantly without arousing suspicion†during her prolonged stay in the United States (Act No. 143: “The Bride of Superman!â€).