Judy Ashton's daughter Debbie died after a head-on collision in Nelson five years ago.
The driver of the other vehicle, Jonathan Allan Barclay, was a disqualified driver who used a witness protection programme to avoid prison by hiding his criminal record.
Ms Ashton had been working with the Sensible Sentencing Trust to sue the police and Department of Corrections over her daughter's death, but last month decided to withdraw her case.
"I have withdrawn the charges, mainly because the realisation, this year it was five years since Debbie was killed, we've been trying to do this for probably two and a half years, and I just need to have the coroner's inquest," she told APNZ.
The prosecution was preventing a coroner's inquest from being held, she said.
"I am disappointed to have pulled out and I may live to regret that, just purely for the fact that it was the principle involved in what I was trying to do, but hopefully through the Kuchenbecker case and the Sensible Sentencing Trust the same outcome will happen."
She hoped the ruling in the Kuchenbecker case would offer some hope to future victims.
"I hope that there is some ruling that gives victims, or future victims, that little glimmer of hope that yes we can hold these people accountable without having to go through all this red tape that we've had to go through."
- APNZ