The Bastard's Betrayal by Katee Robert
She thought it was love.
Rose Romanov is a mafia princess, and everything that entails. Violently over-protective parents. A giant extended family, all ready to kill anyone who looks at her wrong. Learning to run a business that isn’t exactly on the right side of the law. So, naturally, when she meets a nice guy who isn’t in the life, she falls hard… Right up until the she discovers her new boyfriend isn’t a civilian at all.
But he betrayed her.
When Dante Verducci was sent on an undercover mission to evaluate the Romanov family for weakness, he never expected to have an instant connection with their unlikely heir. There’s something fierce and feral about Rose that calls to him. They’re alike, even if they’re both lying to each other during the months they date. Before he could figure out a new plan, Rose finds out who he really is, dumps him, and immediately enters an engagement with the heir of a rival family. Yeah, no, that’s not going to work for Dante.
Now he’ll do anything to reclaim her. Even go to war.