Together they made three New Zealand teams for world events and were part of the top NZ team champions in 2012, 2013 and 2014.
Mable has since been sold and Wiltshire competes aboard Rocky, who she plans to take to the worlds in Denmark in August alongside Kevin Egging and Boy.
"I will be staying with the family who bought Mable when I go back up to the UK, so that's really cool," says Wiltshire.
But first, she has a few things to do here at HOY. Wiltshire has teamed up with Morgan Church for the pairs competition.
"We're probably the underdogs, but that's okay," says Wiltshire, who will ride Sammy at HOY.
And she's happy to carry the same tag with her "pretty solid" crew with whom she will compete in the teams' competition.
Long-term, she has her sights set on winning world titles.
She knows it will be a tough ask, with 30-plus riders more than capable of making the top 14 on any given day.
"Teams, individuals and pairs . . . all of them would be good! To be honest, I just couldn't imagine my life without games, riding and competing overseas."
And while she may still be just a teenager, she's also got a keen eye for business, recognising the value in shipping New Zealand games ponies to the UK to sell.
It costs around $18,000 to fly a horse to the UK.
"People there don't realise just how good our ponies are until they actually see them in action," says Wiltshire.
Mable is a Connemara Welsh cross while Rocky is quarter horse thoroughbred cross - the new "super horse" for mounted games.
"It was tough to sell Mable but I was getting too big for her and the opportunity was there to sell her. I am not sure if I will sell Rocky though - he's very fast and very good so is popular. People know his name before they know mine!"
Wiltshire heads back to the UK in late March and will spend another eight months there before being joined by her sister, doing a tiki tour around Europe, and then home in time for Christmas.