Or, Bob, the male mook of the Big Bad Alice, betrays her for The Hero Charlotte.
Subverted: Alice, The Vamp, pretends to betray the Big Bad Bob, so she can seduce The Hero, Charlie.
Double Subverted...but she winds up falling for him for real, and when it comes time to betray Charlie, she can't.
Parodied: Alice is extremely shallow and falls for Charlie for superficial reasons, having only been with Bob until someone more Badass and better "equipped" came along.
Alice is Genre Savvy and in Bob's service because she wants to meet a heroic man.
Deconstructed: Alice secretly betrays Charlie by rescuing Bob from death, but she makes to clear that she's True Neutral and if she ever sees Bob, she'll kill him. Then she leaves and is never seen again.
The second Arc comes, showing that she used Bob to kill Charlie, so she gains his fallen empire, becoming the new Big Bad.
Big Bad denies all women applying for his organization because of this trope, so he ends up with a reputation of a sexist, his mooks make jokes thinking he's a homosexual, and complain about lack of women around. Big Bad himself dies as a virgin.
Reconstructed: The new Arc comes along, the villianess Darlene has Bob right where she wants him, but Alice makes a Big Damn Heroes moment, claiming that she'll hang around him for a while for entertainment. She becomes the one to kill off Darlene.