Riders have three days to learn their mounts.
Youth squad members from each participating country are assessed on knowledge, understanding and skills with horses as well as their own interpersonal and team-building skills.
Proud Mum Viv Aplin said the squads would tour New Zealand equestrian facilities and take part in workshops.
"She is really looking forward to it," Ms Aplin said.
"She's rapt - she is representing her country."
Aplin will continue with show riding, which is limited to riders aged 14 years to 25 years, and hopes to become an equine physiotherapist.
At the Royal Show in Christchurch youth squad members will be assessed on:
High level of knowledge, understanding and skills in showing horses & ponies.
High level of knowledge, understanding and skills in managing ponies and horses.
High level of knowledge, understanding and skills relating to the equestrian breeds used as mounts in showing within New Zealand Australia and Britain.
High level of interpersonal and communication skills.
An understanding of the role each team member will play as an ambassador for their country and the sport of showing.