We'll Always Have Summer — Jenny Han

Belly has only ever been in love with two boys, both with the last name Fisher. And after being with Jeremiah for the last two years, she's almost positive he is her soul mate. Almost. Conrad has not gotten over the mistake he made when he let Belly go even as Jeremiah has always known that Belly is the girl for him. So when Belly and Jeremiah decide to make things forever, Conrad realizes that it's now or never--tell Belly he loves her, or lose her for good.

Belly will have to confront her feelings for Jeremiah and Conrad and face a truth she has possibly always known: she will have to break one of their hearts.