Warren successfully argued in the High Court on February 3 that his sentence was too harsh.
While behind bars for harassing the woman he told a prison-mate that he wanted to get a craft knife and cut the woman's throat and watch her die.
The prison-mate was shaken by what he had heard and told prison authorities.
Justice Warrick Gendall said the threat to kill came after four years of harassment and intimidation of the woman, which no sentence imposed by the court has had any impact on his "predatory obsession".
Justice Gendall said Warren carried out the threat with a "chilling demeanour", which added to the concern.
"As the witness stated, he believed with every fibre of his being that Mr Warren would carry out the threat."
He said Warren had no remorse for his actions.
"He seems wholly unable to grasp the concept that the victim wants nothing to do with him."
Justice Gendall said he agreed with Judge Garland's concern in his sentencing notes.
"I have very real concerns about Mr Warren and his abnormal obsession with the victim in this matter."
He said he was reluctant to reach the conclusion that the sentence of five years was out of line with similar cases of offending.
He said Warren's offending was less serious than other cases presented by Warren in his appeal case.
He said the fact that the threat had not been made directly to the woman and reached her second hand made it less serious.
Justice Gendall recommended every possible effort be made to provide Warren psychological assessment and treatment in prison.
Warren also tried to appeal against his conviction for threatening to kill, but the appeal was thrown out.
