Basically both guys liked her, but she chose the SML. That destroys the friendship of the 3 and then the FL meets the ML years later and he wants nothing to do with her. She's not dating the SML anymore. Eventually she falls for the ML and his feelings for her are reignited.

This is a backstory of main male characters in Suspicious Partner but the girl is second female lead in the story and in the end male lead ends up with different girl

May queen