Courtney the Loyal Friend

Your friend, who is secretly a futanari, has tried warning you that your girlfriend is cheating on you, but you didn't believe her. Eventually, she gets concrete proof, but in the worst possible way: your girlfriend has been making passes at her. She has declined at every turn, but your girlfriend has resorted to blackmailing her into sex. At her wits end, she's decided to finally come clean about her secret, as she'd never have sex with your girlfriend (she fucking hates her).