The youngster was found with severe lacerations to her neck and chest on a playing field in York last month and died later in hospital.
A 15-year-old girl was arrested after Katie was found injured and charged with murder and possession of an offensive weapon, a knife.
She appeared at Leeds Crown Court via video-link today, sitting next to her solicitor, who confirmed she had written “not guilty” on the indictment in front of her.
The teenager, who cannot be named, did not speak during the 20-minute hearing and only nodded when she was asked by Judge Peter Collier QC if she understood the proceedings.
The girl wore a lilac top with the sleeves bunched up to her elbows and sat with her legs crossed as she listened to what was being said.
A dozen family members were in court and sat at the back, having been brought in through a rear door.
Judge Collier, the Recorder of Leeds, said the teenager’s trial will take place on July 3.
There will be two further hearings before then.
He said she will remain in “local authority accommodation” until the trial.
On Monday, hundreds of mourners donned rainbow-coloured accessories to celebrate Katie’s life at her funeral in York Minster.