"I didn't know what to think," said Elwin. "I didn't know what had happened to Kimberley, but I could see that I had a chance to gain a lot of points on her.
"I had had a shocking start in that race and was working my way through traffic. I was catching [Hawke's Bay's] Rebecca Clark when I spotted Kim on the ground.
"I figured then that I only needed to finish third in my remaining races to claim the title.
"But I didn't want to finish the championship like that and so I continued to push hard."
Elwin won the final race of the championship to wrap up the title by 10 points from Thames rider Natasha Cairns, with Clark finishing third, just two points further back.
"It is an amazing feeling to win my first national motocross title. I know that crashing is sometimes a part of racing, but I still feel sad for Kimberley. She was riding really well."
Elwin had also won the women's class at the annual Motocross Extravaganza in Taupo, on the Saturday of Labour Weekend, although she crashed out of the event the following morning and could not continue in Sunday's MX3-class action, making her title win on comeback from injury at the weekend all the more remarkable.
Other class winners in the women's championships were Turangi's Oceania Hardwidge (junior women's class 1, 85cc two-stroke and 150cc four-stroke); New Plymouth's Mikayla Rowe (junior women's class 2, over-90cc two-stroke and over-151cc four-stroke); and Te Puke's Mary Wanhill (veteran women's, over-30 years).