Slay All Day by Rochelle Paige

Denica Veles has spent more than a decade hunting down the undead as a vampire slayer. The dragon shifter never expected to meet her fated mate while out on a bounty, but there was no denying Trey Kaplan was meant to be hers. She mated and marked the head enforcer of the tiger streak who she’d come to help the same night they met.
Denica was no damsel in distress. She had the experience fighting against vampires that Trey didn’t. But he’d stay by her side every step of the way. Nothing was going to take his new mate away from him now that he’d found her.