Her rival Alexandr Stoianoglo, who was backed by the pro-Russian Party of Socialists, had called for a closer relationship with Moscow.
During the day the president's national security adviser said there had been "massive interference" from Russia in Moldova's electoral process that had "high potential to distort the outcome".
Russia had already denied meddling in the vote, and Stoianoglo, who was fired as prosecutor general by Sandu, has denied being pro-Kremlin.
