Angel by Johanna Lindsey

Hoping to cool off a twenty-five-year-old feud between two neighboring families, Cassie Stuart only succeeds in pouring kerosene on the flames. Both sides have warned her to get out of Texas pronto. . .or they will burn her father's ranch to the ground. What Cassie needs is a peacemaker but she ends up with a widow-maker instead.

He is called Angel , a ruggedly handsome hired gun with eyes as black as sin. Unwanted and unwelcomed by his ungrateful employer, he would just as soon leave Cassie to fend for herself. But a stubborn sense of duty , and a desire to taste the sweetness of her kiss steels Angel's resolve to make Cassie want him, come hell or high water. . .and for more than his gun alone.