Colleen LaRose of Pennsburg has been in custody since she returned from Ireland to surrender to the FBI in 2009.
Her arrest was kept secret until another U.S. woman and six others were rounded up in Ireland months later. A Maryland teen has since been charged in the case.
Court papers show the FBI became interested in the 48-year-old LaRose after she called herself "Jihad Jane" in a YouTube video and said she was "desperate" to help Muslims.
She has since pleaded guilty to conspiracy to murder a foreign target and support terrorists and lying to the FBI.
Her sentencing is set for Dec. 19 in Philadelphia.
Her lawyer did not immediately return a message.