Leitch, the owner of the vehicle, was charged with endangering life by criminal nuisance.
The crash happened on State Highway 6 in Winton when van was being driven back from Queenstown to Invercargill.
Only two people were wearing seatbelts.
Collinson was driving at an estimated speed of 96kmh-108kmh when the vehicle rolled in a temporary 50kmh zone.
Newport described the whole situation as a nightmare and said she still felt anxious when she went to places she used to visit with her daughter.
She said it had been stressful and draining, but in honour of her "baby girl", she refused to collapse.
She had invited both men to her house as she was worried about their mental health but said she was confused after both told completely different stories.
She acknowledged that the pair had taken part in the Right Track programme — a course provided to show dangerous drivers the possible repercussions of their actions and to prevent them from reoffending.
"Thalia wanted so much to live. She was living her happiest moment, flourishing to womanhood.
"Thalia's death should not be in vain. This is the chance to get educated rather than be punished."
Crash victim Rahneisha Peterson also read her statement to court.
The 22-year-old sustained serious injuries which included her neck being broken in two places, a broken pelvis and an ongoing brain injury.
Peterson said her life had changed completely: before, she had been a sociable and happy girl, but now she was full of insecurities, suffering from post-traumatic stress disorder and with a constant worry about her health.
She said she had difficulties concentrating, with her memory, expressing herself and understanding others.
"Reading this today is a huge milestone for me, but I felt you both need to hear what I've been through and am still going through for myself, and I deserve to be heard."
Collinson and Leitch read to court their speeches from the Right Track Programme.
Both said they were remorseful and understood the impact they had had on the lives of those affected by the crash.
Judge Bernadette Farnan acknowledged the pain of the family and the ripple effect of the crash.
She sentenced Collinson to 200 hours of community work, ordered him to pay $4000 in emotional harm to the victims and disqualified him from driving for 18 months.
She sentenced Leitch to 105 hours of community work, taking in consideration he already had completed 95 hours of voluntary community work at SPCA, and to pay $2000 in emotional harm to Newport.
