Ninth Circle by Jordan Silver

When Alyssa Archer returned home a day early from an out-of-town business trip to find her fiancé in bed with the younger sister of her best friend, she didn’t fly off the handle as some might expect. Instead, she retreated to her dining room to partake of the dinner she’d picked up as a surprise.
That night set off a trail of vengeance so dark even Machiavelli would blush.
Garrett Jacobi didn’t expect to feel anything for the up-and-coming financial hotshot when they met. But just days after meeting her for the first he finds himself taking the place of the groom and embarking on one heck of a ride as his new bride makes a swath of destruction through her enemies.