Sandra Layne was found guilty of second-degree murder in the May 18 shooting death of Jonathan Hoffman at their West Bloomfield Township condominium, The Oakland Press reported.
West Bloomfield Township is a Detroit suburb.
The newspaper said the grandmother also was found guilty of possessing a firearm during the commission of a felony.
Layne mouthed "Oh my god," to her attorney and began to cry as the verdict was read, the Detroit Free Press reported.
The newspaper said Layne faces an expected minimum sentence of 14 years in prison, which her attorney, Jerome Sabbota, said was like a death sentence for her.
Layne claimed self defense, but prosecutors said the grandmother stalked the victim around the house before shooting him six times, intending to kill him, the newspaper said.