The Milch Bride (Western Wives 1) by J.R. Biery

Texas is a harsh land in the 1870’s. Jackson Harper loses his wife in childbirth, but is not willing to lose his son. When the baby sickens, he must find a woman to nurse the boy. Unfortunately, the only woman in the county with milk is Hattie Stoddard, the town slut. Despite the protests of his in-laws and housekeeper, Jackson leaves his wife’s funeral to bring Hattie home.

Hattie Stoddard has been a victim of a brutal rape and seen her father beaten and changed forever. By the time she can ride for help, the men who attacked her have told a different story of what happened and the town refuses to believe her. Pregnant and ostracized, she is determined to save her father and the ranch. Then her father and son die.
When Jackson arrives she has nothing left but her shredded pride and the determination not to lose the land. When Jackson tells her she is going with him, she refuses. Finally they strike a bargain, he will pay the taxes and save the ranch if she will nurse and care for his son until J.D. is weaned. But a lot can happen in the milk-year.