10. The Spring Day of My Life (2014) - if I remember right FL and SML (ML's younger brother) are dating, but then she eventually breaks up with him and starts dating the ML.
Just in case I'm wrong I'll also mention Please Be Married. FL is dating a guy, but catches him cheating on her with her best friend. FL and him break up, and he continues to date FL's best friend.
Someone else can choose.