JACKSONVILLE, Fla. -

A Florida woman has pleaded guilty to mailing fake-anthrax letters to the offices of U.S. Sens. Marco Rubio and Bill Nelson.

The U.S. Attorney's Office in Jacksonville said Monday in a news release that 47-year-old Kathryn Cohen Allen pleaded guilty last week. She faces up to 10 years in prison.

According to the release, Allen admitted mailing letters containing a non-hazardous, white, powdery substance to the senators' offices in June 2011.

Allen told authorities she sent the letters to frame her neighbor, a black man whom court records show she had been harassing for several months with accusations that he was sleeping with a married white woman.

Allen had been charged with sending similar letters to other government offices and private citizens, but those charges were dismissed as part of her plea agreement.