His Amish Romance

Amish man Levi Fuller expects to marry his girlfriend Lucy, but her strange behavior following his brother's wedding hints at a deeper mystery. Levi's discovery of her disapproval of his brother's wife threatens to unravel more than just their relationship.
Book 2 Seven Amish Bachelors.
If you haven't started the series yet, it's best to begin with Book 1, The Amish Bachelor.