Heart of Stone. Heart Wish Mail Order Bride, #1

Caitlyn Larrabee was a modern woman before she died. Now she's an angel in waiting. Offered a chance to have a happy life back on Earth if she can answer a deserving man's Heart Wish, she agrees to travel back in time to meet the man who needs her as much as she needs him. Of course, there are rules. She has just seven days to get Lucas Ramsey, a bonafide cowboy, to fall in love with her. And she can't tell anyone, especially her new husband, that she's an angel.
On top of all that, she must avoid, at all costs, the Angel Hunters that will be stalking her -- or risk losing not only her angel powers, but Lucas. Breaking horses for the Army and running cattle on a ranch doesn't keep the darkness at bay for Lucas Ramsey. He's ready to start over. Try again after losing his wife and children to influenza six years ago. So he sends for a mail-order bride.  When Lucas meets Caitlyn he knows she's special but he can't put his finger on why.
She's beautiful, yes, but it's more than that. Little does he know that her time is limited. When he realizes her very life is in danger, he will do whatever it takes to save her.  They may find true love and their happily ever after, but not without sacrifice. Courage. And a love so powerful even a Heart of Stone will beat again.