Family patriarch Hugh Green, who built a fortune in roading, property and construction, died in 2012 aged 80 leaving an estate of $350m.
Maryanne had been chief executive of the family business, the Hugh Green Group, and headed the Hugh Green Foundation, which was set up to give away about $3m annually.
But Companies Office records show she left the business and the trust in the 12 months before her father died.
An employee of the Hugh Green group of companies, who spoke on condition of anonymity, said the legal action related to the children "jockeying for control of things".
Maryanne, lives with her husband, Mark Owens, in Stanmore Bay, in a seaside mansion valued at $1.1m in 2011.
She declined to comment on the stoush, saying: "Thank you for the opportunity but I really don't want to say anything."
A copy of Hugh Green's will shows he left his fortune to the Hugh Green Trust, whose trustees include two of his five children, John and Frances Green, and two lawyers.
John, a horse trainer from Papakura, said: "She's not having a dispute with me. But she's having a dispute with the family, I believe, but I can't comment on that. You'd really need to talk to her."
Frances, from Mt Albert, was on holiday in Melbourne and declined to comment.
Another brother, Gerard Green, said Maryanne was disputing the will through the courts, and affidavits had been filed.
"It's pretty sad, you know. It will just go through it's course, through the courts."
Solicitor Bob Narev, one of the executors of the estate, said a hearing would take place in the Auckland High Court this month. He said he couldn't talk about what was going on as "the case is before the court".
Despite the family's wealth, most of the children live relatively modestly.
Charities Register records show Maryanne Green ceased being a director of the trust in August 2011. John and Frances are trustees, along with family lawyer Bob Narev and barrister Michael Fisher. The trust donates up to $3m a year to medical and disabled charities.
Hugh Green, who was survived by widow Moira and five children, appointed two of his children, John and Frances as executors of the will signed just months before he died, and wanted his fortune to be paid into his charitable trust.
Maryanne and husband Mark Owen's adopted son John Chambers was killed in 2010.
The Hugh Green Trust has given millions of dollars to charity since it was formed in 1998.
Salvation Army public relations director Shane Chisholm said the organisation had been the recipient of donations from the Hugh Green Foundation for a number of years.
The unsolicited donations had contributed towards a life skills programme in South Auckland. additional reporting by Matthew Theunissen
