Nasthalia Luthor
From superman.nu: Supermanica
Nasthalia Luthor
Scheming and sinister rival of Supergirl for many years and a cousin of Lex Luthor (Adv No. 397/2, Sep 1970: "Supergirl Meets Nasty!"; and others), Nasthalia Luthor is often very interested in exposing the secret identity of the Maid of Might.