Fire And Rain By Elizabeth Lowell

Luke hadn't seen Carla for three years. Not since the day he'd so cruelly sent his best friend's kid sister storming from the Rocking M Ranch — and out of his life. Now she was back, lovelier and even more desirable than he remembered. But Luke knew he could never give in to the fire that still raged in his heart. For he'd made a vow long ago, one he was determined to keep — no matter what the price.