Becca's Boy. Amish Sisters Marry, #1

When Becca's rival started showing interest in a certain boy, Becca decided to blackmail Saul into helping her get that boy's attention. She wasn't certain she wanted to marry Thad, but using the secret she learned from her brother, she decided Saul-her brother's closest friend-deserved to be put to this use. Saul had tormented her most of her life. Once she starts her plan, however, she ends up not detesting him.
Saul had long ago admitted his sins to his bishop and asked God's forgiveness, but for reasons he didn't explore, he went along with Becca's blackmail. What follows is a series of adventures and misadventures that put Becca together with Saul more than she'd ever thought. She ends up liking her former tormenter a lot better than the boy whose attention she'd sought and she no longer even cared what her rival did.
Becca fell in love with Saul and, when they argued at the end because Becca believed Saul was making up to her rival, he admits to himself--and confesses to her--that he loves Becca, too.