Nadezhda Yakovlevna Mandelstam (Russian: Надежда Яковлевна Мандельштам, née Hazin; 31 October 1899 – 29 December 1980) was a Russian writer and a wife of poet Osip Mandelstam. Born in Saratov into a middle-class Jewish family, she spent her early years in Kiev. After the gymnasium she studied art. After their marriage in 1921, Nadezhda and Osip Mandelstam lived in Ukraine, Petrograd, Moscow, and Georgia. Osip was arrested in 1934 for his Stalin Epigram and exiled with Nadezhda to Cherdyn, in the Perm region and later to Voronezh. After Osip Mandelstam's second arrest and his subsequent death at a transit camp "Vtoraya Rechka" near Vladivostok in 1938, Nadezhda Mandelstam led an almost nomadic way of life, dodging her expected arrest and frequently changing places of residence and temporary jobs. On at least one occasion, in Kalinin, the NKVD came for her the next day after she fled. As her mission in life, she set to preserve and publish her husband's poetic heritage. She managed to keep most of it memorized because she did not trust paper. After the death of Stalin, Nadezhda Mandelstam completed her dissertation (1956) and some years after was allowed to return to Moscow (1964). In her memoirs, Hope Against Hope and Hope Abandoned, first published in the West, she gives an epic analysis of her life and criticizes the moral and cultural degradation of the Soviet Union of the 1920s and later. The titles of her memoirs are puns, Nadezhda in Russian meaning "hope". In 1976 she gave her archives to Princeton University. Nadezhda Mandelstam died in 1980 in Moscow, aged 81.
The rumor that Salieri poisoned Mozart was propagated in a short play by Pushkin (which Rimsky Korsakoff turned into an opera) and is unlikely to have been true, though it can never be definitively disproven. Mandelstam, a very great poet who was somewhat insane, developed the Mozart - Salieri contrast into a fundamental critical principle distinguishing between "natural" artists like Mozart, for whom creation was easy, and artists like Salieri for whom art was laborious. Pushkin and Rimsky Korsakoff identified with Salieri; Puskin identified his friend the Polish poet Mickiewicz with Mozart, and Rimsky Korsakoff identified Musorgsky with Mozart.
Pushkin's playlet is published along with his "Boris Godunov" and others in Pushkin's "Little Tragedies". I couldn't stand Shaffer's movie, which I think should be avoided. The best article on the rumor is https://www.jstor.org/stable/741525
In his essay "The Child of Civilization" (frm Less Than One collection), on Osip Mandelstam, Joseph Brodsky refers to this work as "a must for everyone interested in the psychology of creativity."