The Macarthur 18-year-old had been tirelessly training for the prestigious competition, which was held at the National Equestrian Centre at Werribee over the long weekend.

Peterson competed aboard her horse Ask No More, known as Buddy.

The pair placed fourth in the junior two star event, after the three phases of dressage, showjumping and cross country.

She had been working up to the competition aboard seven-year-old Buddy and rode him in the young horse event in 2017 in the five-year-old class and in the six-year-old event in 2018.

This year she placed fourth out of a strong field of 20 competitors from across Australia.

She moved up the ranks throughout the competition.

"I came seventh in dressage, then clear and under time in cross country and I had the last rail down show jumping," she said. "I was very proud, my family were very happy for me."

She thanked her family, friends and support crew for their help in the lead up to the event and over the weekend.

Buddy is a Clydesdale Thoroughbred cross and Peterson has extensive lessons with her coaches, fellow eventers Nina and Yona Lloyd at Ballarat and show jumper Jamie Murray.

"I started riding when I was really young," she said.

"I've been riding forever. I want to get as far as I can."

She is currently in year 12 at Hawkesdale P-12.

"I'm going to take a gap year next year," she said. "I'm not sure what I will do. Maybe I will go and work at an eventing stable overseas."

She said she would now take a short break before gearing up for competitions later in the year.

She has qualified for the Equestrian Australia interschool nationals event at Sydney on showjumping horse Another Sportsman, which will be held over the spring school holidays.

She is also the reserve rider for the two star eventing competition on Buddy.

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