24-year-old Alina Tsarnaeva, New Jersey, made the threat against another woman who gave birth to a child from Tsarnaeva husband.
According to the police department, Tsarnaeva allegedly said in a telephone conversation with an opponent "I know people who can put a bomb on you."
Law enforcement officers decided to keep a detainee in custody until the hearings, that is scheduled for September 30.
Two bombs exploded in downtown Boston near the finish line of the on April 15, 2013. Three people were killed, over 260 injured.
A few days after the attack Dzhokhar Tsarnaev was arrested in a suburb of Boston. He is currently in custody awaiting trial. He could face the death penalty if convicted.