Sophia Negroponte stabbed 24-year-old Yousuf Rasmussen to death on Thursday night in Rockville, Maryland, the Montgomery County police said.
The fatal stabbing took place in a cottage at the rear of a larger house in the 400 block of W. Montgomery Avenue. Police arrested her at the scene and charged her with first-degree murder.
Police was quoted as saying rescuers attempted to save Rasmussen, but he was pronounced dead at the scene.
Police said Sophia Negroponte and Rasmussen were acquaintances who had a disagreement inside the home, which led to the stabbing.
John Negroponte served as ambassador to the United Nations, Honduras, Mexico, the Phillipines and Iraq.
He also served as the first director of national intelligence under President George W. Bush and held several other positions in government, including at the State Department.
John Negroponte made several official trips to Africa, meeting with officials to discuss the U.S. policies on Africa.