Something blue / Emily Giffin.

Enhanced descriptions from Syndetics:

From the New York Times bestselling author of Something Borrowed comes a novel that shows how someone with a 'perfect life' can lose it all--and then find everything.

Darcy Rhone thought she had it all figured out: the more beautiful the girl, the more charmed her life. Never mind substance. Never mind playing by the rules. Never mind karma.

But Darcy's neat, perfect world turns upside down when her best friend, Rachel, the plain-Jane "good girl," steals her fiancé, while Darcy finds herself completely alone for the first time in her life...with a baby on the way.

Darcy tries to recover, fleeing to her childhood friend living in London and resorting to her tried-and-true methods for getting what she wants. But as she attempts to recreate her glamorous life on a new continent, Darcy finds that her rules no longer apply. It is only then that Darcy can begin her journey toward self-awareness, forgiveness, and motherhood.

Something Blue is a novel about one woman's surprising discoveries about the true meaning of friendship, love, and happily-ever-after. It's a novel for anyone who has ever, even secretly, wondered if the last thing you want is really the one thing you need.