She auditioned for the movie along with two other women. She says she was the last to audition and afterwards the director said "come with me" to her.
"He took me away from the others and said 'that was perfect and you have the job'."
Stan Walker also plays a part in the movie and Grayson says it was fantastic working with him.
"He's a typical Maori guy - very funny and real casual. I had great chats with him.
"It was fantastic being a part of this movie. When you get to do something like this you don't want to finish working."
Grayson, who has lived most of her life in Christchurch, moved to the Bay to be with her mother last year.
She learnt te reo at a school in Christchurch which she attended from age 11 to 14.
"I love Hawke's Bay. When I first got here I thought Napier was a very pretty place. I like being so close to the sea."
She made her cameo appearance in film as an 11-year- old when she played a small role in the 2008 film 10,000 BC. However, film isn't her only passion. Grayson loves modelling and earlier this year she was Miss New Zealand at the Miss Super Talent of the World modelling competition in Seoul, South Korea.
It was her first international modelling competition where she finished in the top 15 and won the Miss Luxury Award, given to the contestant with the most congenial and bubbly personality throughout the competition.
Grayson got into modelling simply by putting her profile online.
"Chris Robinson took some photos of me and I put them online. An agent saw them and contacted me."
She has since been back to South Korea, representing New Zealand at the Luxury Brand Model Awards. This time it was a female and male model competition and Grayson travelled with a friend from Christchurch.
"I didn't get anywhere but I didn't care about winning. It was very high fashion so I got to see what I have to do next."
She says posing on stage in a bikini doesn't bother her at all. "If you have a beautiful body, show it off. It's not like I'm a stripper, it's a fashion show."
Now she is trying to decide between two pageants being held at the end of August. The first is in Italy and the second Romania.
"I'm leaning toward Romania simply because it is a male and female pageant and that means I would have a travelling partner. I've seen the itinerary and it looks amazing - boat cruises and city tours.
"I love what I'm doing - it's an unexplored experience every time and it's awesome."