Reeva’s father, Barry, 79, was too unwell to travel for the Parole Board hearing.
Ms Koen said Reeva’s parents insisted Oscar Pistorius, 36, “never told the truth” about her death.
Gun aficionado Pistorius recounted at his trial that he thought Steenkamp was an intruder when he shot her multiple times through the bathroom door with ammunition designed to inflict maximum damage to the human body.
He was jailed in 2016, initially for a six-year term, but that sentence was increased to 13 years after an appeal by prosecutors who argued that the initial sentence was too lenient.
Pistorius, who had both legs amputated as a baby, reached the pinnacle of his fame in 2012 when he became the first double amputee to compete against able-bodied athletes at the Olympics, reaching the 400m semi-finals in London.
In a court case that attracted worldwide attention nine years ago, the athlete shuffled through the court without a prosthesis to show how vulnerable he was to the threat of an intruder.
He burst into tears when he told the court that he had wanted to protect Steenkamp when he fired the shots. The prosecutor at the time accused him of using emotional breakdowns to avoid questioning.