What are the motifs in Something Blue by Emily Giffin?

Karma is a recurring idea. Karma shows itself to Darcy in a number of ways in the story. When Darcy finds Dex and Rachel together, karma is rewarding Darcy twofold. Darcy has betrayed Dex by kissing one man and making out with another while still Dex's girlfriend. When Darcy and Dex become engaged, she initiates an affair with Marcus and is pregnant. Darcy betrays Rachel by pursuing a man she knows Rachel likes and has dated. One could say Darcy is also reaping her behavior as a child when she asked Ethan to be her boyfriend knowing it would hurt Rachel.