Very specific request

Does anyone here know a story where two people who hate each other starting dating in secret and don't tell a third person they both know and are friends with and some point the person finds out?
E.g. in a trio two hate each other but are friends with the third
Can be friends, enemies, any genre. As long as there's the third person involved who's lowkey betrayed (i want the pain).
Book, movie, show, manga, idc. PLEASE.