The Cyprian

A cozy, cottage-core Regency fantasy perfect for fans of BridgertonElena Whitstone and her seven brothers, abandoned by her mother, find themselves with a new stepmother.  At first she seems more neglectful than evil, until just after Christmas she proves herself to be worse than evil; she is an actual magician, a Master of Water, who attempts to muder Elena's seven brothers when they are skating.  When they survive that attempt by transforming into swans, she drives them away.  But the shock of having all of his heirs perish in a frozen pond is too much for Elena's father.  He dies, and his widow is abruptly confronted with the inconvenient truth that the estate is entailed, and she not only must leave, she is lawfully in charge of Elena. Furious, and possessing "only" what was gifted to her during her marriage, the stepmother retreats to Bath, to take up residence in the luxurious townhouse that was bought for her, and resume her former profession as a "Cyprian, " a very exclusive courtesan, with Elena reluctantly posing as a page-boy and her servant.  Nothing lasts forever, of course, and three years later, Elena is rapidly maturing too much to continue that ruse--and the stepmother is facing the ravages of time.  The stepmother concocts a plan to establish an exclusive brothel and regain her wealth by selling Elena to the highest bidder.
Alone, Elena must not only find a way to save herself, but to reverse the spell that has transformed her brothers. The latest in Mercedes Lackey's Elemental Masters series is a stand-alone romantasy based on Hans Christian Andersen's The Wild Swans.