She said a young man was taken in "a horrible, horrible way".
"At the end of the day, nothing has been done. The killer is still out there."
In 2015, it was revealed a private investigation - launched by Kylee - had ended because of a lack of cash.
The Sensible Sentencing Trust, working on behalf of Kylee, had also approached four private investigators in a bid to find the killer and bring them to justice.
A member of the PI team, Mike Crawford, revealed in 2015 that the hunt had been dropped. "The investigation has basically stopped. It's finished," he said.
Former trust spokeswoman Ruth Money confirmed at the time that a lack of funds had curtailed the bid.
"Sadly, they've [PIs] stopped because there's no more funding," Money said. "The family can only spend so much."
Money told the Sunday programme that "fresh lines of inquiry were identified and handed to police" after the investigation.
"Without a doubt, there is compelling evidence that the police haven't investigated, and should," she said.
Asked why police had not pursued the leads, she said: "It could be resourcing, it could be a risk of reputation. I don't care. Kylee doesn't care. This is about justice for Scott. It needs to be handed to a completely new police team, and someone needs to be held accountable."
Kylee and Scott's sons Hunter and Drover are now aged 12 and 9, and Kylee has another son, Husky, now 4, with her new partner Kent Martin. Kylee said that when Hunter started school, another child said, "I saw your dad bleeding on the front page of the newspaper".
"It's those things I was trying to protect my children from," she told Sunday.
"All I can do is try to stay positive, surround them with as much love as you can, and lots of cuddles."
Scott Guy's parents spoke to the Weekend Herald last month in the lead-up to the anniversary, saying they thought about him every day.
"You can say it's 10 years since Scott was killed but it's actually 3653 days on his anniversary and every one of those days we think of Scott," Bryan Guy told the Weekend Herald.
"If we dwell on why or what if, it destroys you. Building resilience is where our focus is with our children and grandchildren - showing them the choices we make and how we react, they watch us all the time, let alone what we say.
"We want to be a good example to them and help them build strong relationships - to help them cope with life and the things that get thrown up. We live for helping our kids."
"It feels like Scott was here just yesterday but then other times it feels like it's been forever. I find it difficult when I see what Scott is missing out on but I am thankful for the time spent with Hunter and Drover. Being with them feels like you are close to Scott," she said.
Anna Guy's ex-husband, Ewen Macdonald, was charged with the murder but was acquitted.
Scott was the second eldest of four children — him, Nikki, Anna, and Callum.
After working on several farms and a short stint studying for a diploma in agriculture at Massey University in Palmerston North, he left for Australia to work on a farm. There he mustered cattle on horseback, fulfilling his dream of being a cowboy.
He returned to the family farm Bryerburn in 2003 and was put in charge of the crops and calf-rearing while Macdonald managed the dairy side. Superficially the working arrangement seemed fair and equitable but Guy's death later revealed tension and rivalry between the pair.
Guy met 18-year-old Kylee Bullock, who was training to be an early childhood teacher, at a Havelock North pub after a rodeo.