"She wielded her immaculate beauty with sly wit in Mr. Buñuel's "Belle de Jour" (1967), as a bourgeois wife who vanquishes her frigidity by secretly turning tricks in a brothel, but conveyed an even more supple emotional transformation in Mr. Buñuel's "Tristana" (1970), based on Benito Pérez Galdós's novel about a corrupted innocent."