"I came from a small rural area where running was not really considered a sport," she says. Running was just something you did to help rugby practice."
It was only during her penultimate year in high school where her eyes were opened to the possibility of endurance running. It was then Mercury Bay Area School decided to enter the Hillary Adventure Race - a gruelling five-day hiking adventure racing challenge. She enjoyed the training around the Ruapehu track but wanted more: "I wished I could go a bit faster" she admits.
On completing the challenge, she discovered the possibility of running races over a similar terrain and she targeted the 20km Goat Adventure Run - for her multi-terrain running debut. Taking on the 20km challenge on the slopes of Mt Ruapehu, which includes 1000m of vertical ascent, she triumphed and so a new addiction was born.
Around the same period Ruby was also undergoing a personal tragedy. Her father, David Elliot, who ran a wedding business, was dying of brain cancer and running became a rock to cling to during this harrowing period of her life.
"I became very serious (about running) and it was coping mechanism," she says. "It was good for my mental health."
Enthused by her new-found sport she competed in trail and endurance marathons every other weekend and despite her relatively tender years - where athletes are not expected to reach a peak until their mid-thirties - Ruby has gone on to earn a reputation as one of New Zealand's premier ultra-endurance performers.
A two-time winner of the internationally recognised Tarawera Ultramarathon (in 2013 and 2015) and a four-time Kepler Challenge champion she has also enjoyed success overseas winning the 2013 The Otter African Trail Run in South Africa.
As a junior she was also persuaded to compete in the World Mountain Running Championships in Slovenia - where despite the short distance of just 4km - she further underlined her versatility by finishing 11th.
So why does she feel so well suited to the trails?
"Growing up in the bush, I think I have a natural ability for more technical running," she says. "I spent a lot of time playing around in rivers and I have a natural endurance to keep going for a long time."
With an ability to excel over varying terrains, Ruby appears to have fazed by very little. Yet she has one Achilles heel - altitude - which may have changed the whole direction of her running career.
Running at the 80km Ultra Du Mont Blanc in France in 2014 and struggling with altitude sickness she tripped and fell almost tearing the Vastus Intermedius muscle - one of the quadriceps muscles - off the tendon.
The injury was serious. It forced her on the sidelines for several months and to this day she has lost "the majority" of the muscle in her leg.
"I thought for a while I might have to stop running," he says. "For a long time I had a lot of trouble running hills and I couldn't put weight on my leg. When cleaning, I used to have crouch down with a dustpan and brush and lean my leg straight out like Spiderman because of the pain."
Yet Ruby is a resilient soul and refused to give in. She changed the emphasis to shorter races and the move has proved profitable as she won the 2015 Wellington Marathon in 2:49:08.
"I'm still not as good as I used to be on the technical sections and I don't have the power on the uphills," she says. "I don't feel quite as confident tearing up the mountains and I also know if I land wrong on my leg, I can hurt it. But I'm back up to 160km (training) weeks and now I can do a lot of the hills. I now know how to train on (the injury)."
Self-coached throughout her career because she likes to flexibility to change things herself she nonetheless draws from some of the learnings of her husband Kristian Day - himself a 2:31 marathoner - who is coached by Craig Kirkwood.
After a period living in Kristian's home city of Napier - where she worked as an assistant house manager and he was a student - at the beginning of the year the roles were reversed as the pair moved to Wellington.
In the capital, Ruby returned to university to started a physics and environmental science degree while Kristian has taken up a teaching role.
Following Ruby's fresh approach to the sport she targeted a 2:40 marathon at Gold Coast in July, however an upset stomach forced her to quit. Hugely frustrated by the experience in Queensland she turned her attention to the New Zealand Cross Country Championships at Auckland's Domain, where she bounced back to produce a dominant display and snare the prestigious title from the front.
"I was keen to make use of the form I had built with my Gold Coast Marathon training block, so I refocused and targeted the New Zealand Cross Country Championships," she explains.
"I'm quite competitive, I always race to win. I know I am not that fast, but I just wanted to take out the race quite hard rather than making it come down to anything quite tactical. I thought more girls would come with me and it was pretty satisfying to win."
Her most immediate target is next month's New Zealand Road Championships in Christchurch followed by the Kepler Challenge later this year and a return to her beloved trails. Yet the 26-year-old is unquestionably at a crossroads in her career development.
"I'm a bit confused as to which direction I want to go," she says. "Because I am studying continuing on the road fits more easily, although I'm always tempted to do a big adventure trail race as well."
Ruby would also "love" to run more marathons although she is concerned the stomach issues which blighted in her Gold Coast and also troubled her when finishing seventh in the 2015 Auckland Marathon may prove a bar to fulfilling her potential.
Yet whatever the future holds one things is more certain; Ruby will be running in one form or another.
"Running has given me so much," she says. "I had several years competing internationally which was really exciting, but the biggest benefit is for my mental health. That internal satisfaction after completing a hard session keeps me happy."
