Louisa Gardner’s Ngrimmirra centres on two sisters, one of whom moves to the city for university.
“It looks at the changing dynamic between the pair over the years and how their relationship is influenced by their mother, their societies and their identities,” she said.
“It’s basically the story of them coming together and then drifting apart as sisters can do over time.”
The 16-year-old Booragoon resident said it was her first novella-length project and that she was looking forward to tackling more in future.
“It was interesting in that I couldn’t plan the story in as much depth as I’m used to,” she said.
“When I set out to write it I didn’t have any plans for how it would end but when I got there the ending presented itself naturally.”
As one of three finalists, Louisa will travel to the Somerset Celebration of Literature in Brisbane later this month to take part in three days of events.
As part of her prize, she will also receive personalised advice on her winning manuscript from Penguin Group Australia.
The national winner will be announced during the festival.