The wife of Felix Leiter was Della Churchill, usually referred to simply as Della Leiter. She appears most prominently in the 1989 James Bond film Licence to Kill, where she marries Leiter and asks Bond to serve as best man.
Della’s wedding night becomes the film’s emotional turning point. Drug lord Franz Sanchez, seeking revenge against Leiter, has him brutally attacked and leaves him badly injured. Della is murdered, prompting Bond to abandon his official assignment and pursue Sanchez personally. The tragedy explains the film’s title and its unusually personal revenge story.
Della is played by Priscilla Barnes, while Felix Leiter is played by David Hedison. A common mix-up is to confuse Della with Tracy Bond, James Bond’s wife, or with later versions of Leiter’s family in continuation novels and comics. In the main cinematic story, however, the canonical answer to the question is Della.