Cimarron Sunset by Peggy Darty
Christian romance. Set in southern California in the time of full skirts and crinolines. A seamstress lives with a wealthy family as their personal seamstress in repayment for damage done to a dress at her family shop, and falls head over heels for the son of the family in the meantime. His mother isn't happy about this, and becomes a monster in law before they even get that far.