Two Dances and a Duke by Eloisa James

Shamed for her curves and plagued by a Mean Girl, Bea is miserable – until she triumphs over social disaster and wins the hand and heart of a duke. One of Eloisa James’s most exuberant and emotional novellas.
Miss Beatrice Valentine is having a horrible first Season, shamed for her curves by Lady Regina Haywood.
Despite Regina’s attempts to make Bea a wallflower, Bea finds herself torn between Regina’s fiancé, the rakish, quick-tempered Lord Peregrine, and Regina’s brother, the war-hero, the Duke of Lennox.
Bea is determined to marry a kindly man, and certainly no one close to Regina. But both of these gentlemen are determined to seduce her and one will succeed.