"It's been a lot of hard work - when you have a job, and you've got your own family, it was hard."
As well as launching Airini Karauria - Her History, Her Life, Her Descendants, a unique portrait of Airini by the acclaimed painter Gottfried Lindauer was also unveiled, the first time most family members had seen it.
Ms Fearn said it was important for her whanau to know their heritage.
"She was a strong ally or a formidable adversary, depending on where you stood with her.
"She was an incredible woman in an era when Maori women ... only had a quiet strength."
Her biography of Airini, who was born at Puketapu in 1855, began about 40 years ago after one of her children began talking about family history.
She gathered information including oral whanau history, court documents and newspaper archives until two years ago, when she decided it was time to put it all together.
Airini's father was Ngati Kahungunu chief Karauria, who died when she was just 13 while pursuing Te Kooti in Poverty Bay.
Airini became heiress to vast tracts of land, including what was then the Ngatarawa Farm, and having learned English from a young age she grew to become a committed advocate and defender of her people in the region.
After marrying an Irishman and spending time in the English royal court, Airini spent three decades defending her people's land against what she saw as unscrupulous claims.
She died in 1904 at age 55 of cervical cancer at the couple's Otatara family homestead near Taradale. Anyone interested in the book can contact Ms Fearn on 027 814 1970.
