The Georgian Rake — Alice Chetwynd Ley

Reckless, seductive, she defied the customs she was raised to honor to prevent her sister's wedding...

Amanda Twyford had to face the unwelcome news that Charles Barsett would wed her sister Isabella. Charles' roguish reputation made such a marriage unthinkable to Amanda-but not to Isabella, a dutiful daughter whose head was turned by Charles'title and wealth.
It was left to Amanda to prove that Charles Barsett's reputation was more than mere gossip. She would go to any length to prevent this arranged marriage: hatch wild schemes, enlist other men to help her, break into his home-or even wed the Georgian Rake herself...!