The Dreadful Debutante. Regency Royal 16

Arranging a season for an unruly young lady whose habit was to enter drawing rooms by sliding down banisters presented a challenge at best - especially since the hoydenish Mira had a sister of incomparable grace and beauty. Mira wasn't daunted at all by the local society and its ridiculous marriage mart. Her heart belonged to Lord Charles, who had been the object of her dreams ever since she was a child.
Alas, Charles had eyes only for her ever-perfect sister, Drusilla. Along the sidelines, the Marquess of Grantley was enjoying Mira's jealous antics - although pushing her sister into the fountains had practically ruined her social cachet. It was up to him to restore her to respectability and make her an eligible bride once again. Yet when he succeeded, the lovelorn Marquess began to wish he had left well enough alone.