Which classic Disney film villain was created in 1956 by the British playwright and author Dodie Smith?

From a 2021 Times article by Sarah Bahr:

Created by the British playwright and children’s novelist Dodie Smith, Cruella was born in a 1956 children’s novel, “The 101 Dalmatians.” Yes, the skunk hair and selfish nature were there from the start, but the original Cruella was more of a spoiled socialite than a Maleficent — at least outwardly — and conveyed a preternatural calm. She doused her food in pepper, was expelled from school for drinking ink, boasted of having the loudest car horn in London and was married to a wealthy furrier — though not for love, apparently.