His to Protect by Julia Keanini

Emma Heathcliff isn’t safe. She’s witnessed a drug deal that could put one of the most powerful men in the nation behind bars, and the man has already proven he is ready to continue to commit crimes in order to keep his freedom. When witness protection doesn’t seem like an option, Emma has one choice. She has to spend twenty-four/seven being guarded by the gorgeous Jax Hightower, her best friend’s brother and the guy who has hated her for the past fifteen years.
Jax Hightower has already got Emma pegged. He’s met plenty of her type. She’s a spoiled rich girl who thinks too highly of herself to date his little brother who has pined over her for years. When Jax’s family asks him to guard her because of his extensive training, thanks to his years as a Navy Seal and now as a bodyguard to the rich and famous, his answer is easy. No. However that no doesn’t stick, and Jax finds himself flying across the country to spend day in and day out by the side of the woman he can’t stand.
But a few hours into the assignment and Jax discovers Emma isn’t anything like he thought she’d be. She’s kind, hardworking, and smart. Where is the girl he was sure she was? No longer worried about having to guard a woman he dislikes, Jax finds himself falling for Emma–the girl his brother has loved for half of his life, the one woman Jax can never have.