A video recording of a police interview with the girl was played at a court in BradforSEXd, northern England, where Johnson is on trial after denying two counts of sexual activity with a child.
Johnson, who was fired by English club Sunderland last week, has already pleaded guilty to grooming and another charge of sexual activity with a 15-year-old girl.
Asked in the interview what Johnson knew about her, the girl said he knew how old she was, what school year she was in, and where she sat at Sunderland matches. She said Johnson also knew her date of birth.
She had been questioned over why she asked friends to lie about what allegedly happened with Johnson.
"I was scared that people wouldn't believe me," the girl said.
Johnson has played 12 times for England, and also at club level for Manchester City and Middlesbrough.