Something Blue by Emily Giffin

Following the smash-hit Something Borrowed comes story of betrayal, redemption, and forgiveness
 
Darcy Rhone has always been able to rely on a few things: Her beauty and charm. Her fiance, Dex. Her lifelong best friend, Rachel. She never needed anything else. Or so she thinks until Dex calls off their dream wedding and she uncovers the ultimate betrayal. Blaming everyone but herself, Darcy flees to London and attempts to re-create her glamorous life on a new continent. But to her dismay, she discovers that her tried-and-true tricks no longer apply—and that her luck has finally expired. It is only then that she can begin her journey toward redemption, forgiveness, and true love.