So you want to write a demoiselle novel!
Fortunately, the fundamentals of the demoiselle novel are pretty simple. You need one demoiselle, one step-parent (usually an evil one), two evil conspirators, one evil seducer, and one hapless suitor. Theoretically this adds up to six characters, but there’s normally some overlap between the evil seducer, the two evil conspirators, and the stepparent.
Overlapping the villains makes things simpler, but sophisticated authors mix things up by doubling some roles, or by overlapping one of the villain roles with one of the non-villain roles. In Henry James’ novel there are two demoiselles (one of whom is also the stepmother), the evil conspirators are the birth parents rather than the stepparent, and Warburton is the hapless suitor, first of the stepmother-demoiselle, and then later, of the stepdaughter-demoiselle. Warburton is a farcical anti-Humbert: stepfather Humbert Humbert courted the mother to get next to the daughter (his stepdaughter), but Warburton courted the stepdaughter to get next to the stepmother (who would become his own stepmother-in-law).
Pansy Osmond has two hapless suitors but no evil seducer. This is possible because 19th century novels from the United States, where sex had not yet been discovered, tended to avoid any hint of actual intercourse. At age 20 Pansy Osmond was too old to still be a demoiselle rather than an old maid — but there she was in the convent, cute as a bug and utterly adorable. Gilbert Osmond was trying ever so hard to be a sophisticated, decadent European, but he was just an American working out of an idiot book and couldn’t get anything right. (Isabel Archer was far too old to be a demoiselle when he married her, too, but did he notice that?)
|Novel||Les Liaisons Dangereuses, Choderlos de Laclos||Lolita, Vladimir Nabokov||Portrait of a Lady, Henry James|
|Demoiselle||Cécile Volanges (convent girl ™)||Dolores Haze (American girl ™)||Pansy Osmond, American convent girl / Isabel Archer (American girl ™)|
|Evil conspirators||Mme. Merteuil and Vicomte de Valmont||Humbert Humbert , Clare Quilty (competing)||Gabriel Osmond, Mme. Merle|
|Evil seducer||Vicomte de Valmont||Clare Quilty, Humbert Humbert||Gilbert Osmond (Isabel) / none (Pansy)|
|Stepparent(s)||Mme. Merteuil and Vicomte de Valmont (friends of the real mother who both counsel Cécile)||Humbert Humbert||Isabel Archer / Lord Warburton (potential stepson-in-law, stepmother’s ex)|
|Hapless suitor||Chevalier Dancey||Richard Schiller (who gets Dolores in the end, but in seriously damaged condition), Clare Quilty, Humbert Humbert.||Caspar Goodwood, Lord Warburton, Ralph Touchett (Isabel) / Edward Rosier, Lord Warburton (Pansy)|