She Was Pretty - the ML and FL were friends / had a bit of a crush on each other when they were young. The FL was conventionally attractive and the ML was not. The ML moved abroad and when they're adults he asks to meet the FL again. He has become conventionally attractive and she is no longer conventionally attractive. Out of embarrassment the FL asks her conventionally attractive best friend to pose as her in order to meet the ML. The friend falls for the ML and dates him while continuing to pose as the FL without telling the FL. Meanwhile the ML and FL are coworkers with friction, but they're also developing feelings for each other. The ML confesses his feelings to the FL while still dating the SFL.
The Princess' Man - the ML is engaged to the FL's friend who likes him
Story of Yanxi Palace - the FL is very close with the ML's wife, who dies before the ML and FL's romantic storyline fully begins
Moon Lovers: Scarlet Heart Ryeo - the FL is close with the wife of one of the SMLs and she has a romantic storyline with that SML while the wife's health deteriorates and she ultimately dies
High Society - the FL's friend, the SFL, falls for the ML first
The opposite (two male characters who are friends or allies fall for the FL and the ML sort of has an affair with the FL):
