Eve Teschmacher was a character in Superman: The Movie, and Superman II. She is Lex Luthor's assistant and perhaps girlfriend.

Superman: The Movie

She is very sexy, and attractive, and that's why Luthor chose her as his girlfriend. Ms. Teschmacher acts as a supporter to both Luthor and Superman. Despite being Luthor's girlfriend, she has feelings for Superman, and she later saves him from drowning after Luthor outsmarts him. She also kisses him. ("Superman: The Movie")

She is the only person to kiss him in the movie.

She helps Lex to escape prison by flying a balloon over the prison with a rope ladder. Lex climbs out, and together they go to the arctic where they enter Superman's Fortress of Solitude. There, they learn about the three Kryptonian villains led by General Zod in the Phantom Zone. She is eventually pushed off a ledge during the final battle in the fortress by Lois Lane. ("Superman II")

Superman: Red Son

Eve Teschmacher was Luthor's secretary, and it was she who admitted people to see him. ("Superman: Red Son")

She appears off-panel in the comic, constituting a brief cameo.

Smallville

Tess Mercer may be a version of Ms. Teschmacher, due to the similar name and her her status as Luthor's second in command. Her character may be merged with that of Mercy Graves.

In season 8, Tess Mercer has taken over Lex's job and place in the mansion. She is also the new editor of the Daily Planet.

Trivia

In professional wrestling, the female wrestling characters "Eve Torres" and "Miss Tessmacher", formerly WWE Diva's Champion and TNA Knockouts Champion respectively, both served in "sexy secretary" roles under evil men (John Laurinaitas and Eric Bischoff) in the year leading up to their becoming champions.

Torres also went on to try and seduce John Cena, who is such an all-powerful babyface he is regularly referred to as the "Superman" of the WWE.