Her 18-year-old boyfriend, James Neal Perkins, of Tyler, was arrested at Goodwill Industries, where he works.
Both teens have been charged with conspiracy to commit murder. Conviction is punishable by 2-20 years in prison.
Tyler police spokesman Don Martin told The Associated Press that officers have a witness who came forward with information about the alleged plot. Martin declined to release specifics, but said nobody was hurt.
Perkins also was arrested on an outstanding warrant for a false alarm, over threats made to Chapel Hill High School, where he was a student.