The Wager: A Pride and Prejudice Variation (Accomplished Ladies #1)
L.K. Rigel

While the rest of the Bennet ladies are away from Longbourn, Charlotte Collins invites Mary to stay at Hunsford. Mary accepts, determined to quash her tender feelings for Mr. Collins, but she's is quite unprepared for the handsome and charming Lt. Col. Carleton "Carley" Quartermaine, visiting Rosings Park with Colonel Fitzwilliam.
The man is utterly unbelievable, entirely insufferable, and completely unstoppable.
Then prim Mary is scandalized to discover that she is the subject of a bet among gentlemen. Well, two gentlemen and one "lady" ~ mischief maker Caroline Bingley. The lieutenant colonel's smile may send shivers to Mary's very soul, but she vows she'll never let him make her eat her words regarding female virtue.