Nymphet

noun/aesthetic
nymph・et
nim-'fet
feminine

A sexually precocious girl barely in her teens.

Nymphet, also sometimes referred to as Coquette or Vintage Americana Coquette , is an aesthetic based on a character trope originated by Vladimir Nabokov in his book Lolita, published in 1955 and its movie adaptations from 1962 and 1997. Nymphet is an illusion created in the mind of Humbert Humbert, the (unreliable) main character.
It was used by Humbert as a way to justify his predatory actions towards 12 year old Dolores Haze, his victim.