Campbell Estate heiress Abigail Kawananakoa — the wealthy descendent of Hawaiian royalty whose private life was thrust under a spotlight during a bitter fight over her $215 million trust fund — died Sunday at the age of 96.

Hailama Farden of Hale O Na Alii O Hawaii and Iolani Palace executive director Paula Akana announced Kawananakoa’s death in olelo Hawaii at the front gate of Iolani Palace this morning.

“With profound sadness, the Kawananakoa family, the Hale O Na Alii O Hawaii and the Iolani Palace announces the passing of Her Royal Highness, Princess Abigail Kinoiki Kekaulike Kawananakoa at 6:45 p.m. last night,” Farden said. “We join each other in a period of mourning.”

She died of natural causes, an Iolani Palace spokesperson said.

The James Campbell Company issued an emailed statement this afternoon: “Abigail Kekaulike Kawananakoa was a faithful and supportive shareholder of the James Campbell Company and she will be remembered fondly by the Staff, Management, and Board of Directors. Throughout her long and productive life, she was a champion of the Hawaiian people. Our deep condolences go to her family.”

Gov. Josh Green ordered that the U.S. and Hawaii state flags be flown at half-staff at all state offices and agencies until sunset on Sunday to honor Kawananakoa.

“Jaime and I are deeply saddened by the loss of Princess Abigail Kinoiki Kekaulike Kawananakoa,” Green said in a news release. “Abigail bore the weight of her position with dignity and humility, enriched the lives of everyone she touched, and like so many alii who came before her, she has left a legacy dedicated to her people in perpetuity. Hawaii mourns this great loss, and our aloha and heartfelt condolences go out to her entire ohana and all who had the privilege of knowing Princess Abigail Kawananakoa.”

Honolulu Mayor Rick Blangiardi sent a statement this afternoon following Kawananakoa’s death.

“I was saddened to learn this morning of the passing of Princess Abigail Kinoiki Kekaulike Kawānanakoa,” Blangiardi said in a news release. “She epitomized Hawaiian royalty, and spent a lifetime dedicated to supporting the Native Hawaiian culture and its causes. She did it with wisdom, dignity, grace and humility. On behalf of the City and County of Honolulu, we wish to extend our most heartfelt condolences and aloha to the Kawananakoa ohana in this time of mourning.”

Kawananakoa, the great-grand-niece of Queen Kapiolani, was a prominent, sometimes-controversial figure in the islands, known as a financial supporter of Native Hawaiian culture and causes and an activist who was not afraid to go to court in her later years to fight for what she believed in.

Often given the title of princess because of her royal heritage, Kawananakoa in 2001 created the Abigail KK Kawananakoa Foundation, a charity to administer about $100 million for Native Hawaiian causes after her death.

At the same time, Kawananakoa spent tens of millions of dollars on her hobby of quarter horse breeding and racing. Her success on the track made her the sport’s top female breeder and led to her 2018 induction into the American Quarter Horse Hall of Fame.

Kawananakoa’s latter years were thrown into turmoil after she suffered a stroke in June 2017. For the next several years, the woman’s soon-to-be spouse and long-time attorney faced-off in court over control of her fortune and the possible fate of her foundation charity.

A psychiatrist would end up declaring Kawananakoa incapable of handling her own financial affairs, and a judge would appoint a conservator to oversee the handling of her personal money.

The fate of the charity remains uncertain, however, as several issues connected to the estate are still being litigated.

Born Abigail Kinoiki Kekaulike Ellerbrock in 1926, her parents were Lydia Kamakaeha Liliuokalani Kawananakoa and William Jeremiah Ellerbrock. They divorced after just two years, and the girl was legally adopted by her maternal grandmother, Abigail Wahiikaahuula Campbell Kawananakoa, who was married to Prince David Laamea Kahalepouli Piikoi Kawananakoa.

The girl would attend Punahou School and Shanghai American School in China before graduating from Notre Dame School in Belmont, Calif., in 1943. She attended Dominican College in San Rafael, Calif., for two years before transferring to the University of Hawaii.

Kawananakoa, known as Kekau to her friends, inherited her wealth as the great-granddaughter of James Campbell, 19th-century businessman from Ireland, who made his fortune as a sugar plantation owner and one of Hawaii’s largest landowners.

After college, she lived in Europe, traveled and spent several decades moving between her primary residence in California and Hawaii.

In the islands, she lent her support to a number of Native Hawaiian institutions. As long-time president of the Friends of ‘Iolani Palace, an organization her mother started, Kawananakoa played a role in the restoration of the palace that was built by King David Kalakaua.

Often described as strong-willed and opinionated, Kawananakoa crossed the IRS on occasion and was no stranger to controversy.

In February 1997, she filed for bankruptcy protection. Debts listed in the Chapter 11 filing included more than $5 million to the IRS for taxes, penalties and interest.

In 1998, she created a stir when she sat on a fragile 115-year-old palace throne during a Life magazine photo shoot. The controversy led to the resignation of Jim Bartels, Iolani Palace managing director and curator.

In 2013, a request by Kawananakoa to build a new tomb at the Mauna Ala royal mausoleum generated backlash from some who questioned whether her lineage qualified her for such an honor. The state Board of Land and Natural Resources eventually granted her the right to be buried there.

A lifelong equestrian, Kawananakoa bred her first quarter horse for racing in 1980, and her success in the following decade made her one of the sport’s top owners and breeders.

Her stallion, A Classic Dash, won the All American Futurity in 1993 and her horse Evening Snow broke a 27-year record to become “the fastest horse in the world,” in 1995. Kawananakoa would win five world championships and consecutive titles as champion owner in 1994 and 1995.

Kawananakoa is the industry’s all-time leading female breeder, producing earnings of more than $10 million, according to the American Quarter Horse Association.

“Horses have always been the next-most important thing in the world to me, besides my friends and Hawaii,” she is quoted as saying on her Hall of Fame web page. “What can I say? I’m catching the rainbow.”

During her lifetime, the largest share of her philanthropy went to Colorado State University, where she donated $20 million to help build a veterinary teaching hospital and $3 million to fund an endowment for equine orthopedics.

Most, if not all, of her top racing achievements came in the 1990s, but she continued to breed and run horses to earn more than $3 million in winnings since 2000, according to the Equibase horse racing statistics website.

But in recent years the woman was losing as much as $4 million a year on her Nuevo, Calif., horse breeding and ranching operations, court records indicate.

As Kawananakoa grew older, she used her wealth to fuel her activism in the islands.

In 2005, she filed suit demanding the return to Bishop Museum of 83 Hawaiian artifacts that were reburied in Kawaihae or “Forbes Cave.” The items were finally returned after the case was settled out of court.

She later emerged as an opponent of the Honolulu rail project, paying for a full-page ad in the Washington Post for former Gov. Ben Cayetano asking President Donald Trump to halt federal funding. She also unsuccessfully sued to invalidate rail project votes from Honolulu City Council members who failed to disclose conflicts of interest.

Kawananakoa opposed the controversial Thirty Meter Telescope planned for the summit of Mauna Kea. She not only publicly criticized UH for poor management of the Mauna Kea astronomy precinct, but she donated thousands of dollars to TMT protesters and filed a lawsuit seeking records related to the hiring of TMT contested case hearing officer Riki May Amano.

In 2015 Kawananakoa filed suit against the Office of Hawaiian Affairs Board of Trustees in a unsuccessful attempt to invalidate the three-year contract renewal of former CEO Kamanaopono Crabbe.

Her activism ground to a halt when she fell victim to her 2017 stroke. The crisis prompted longtime lawyer, James Wright, to ask the court for control of the woman’s estate in a move that was spelled out in a successorship plan set up by the heiress in case she became incapacitated.

But with her partner of 20 years, Veronica Gail Worth, by her side, Kawananakoa insisted she was fine and fired Wright. She then married Worth, who took her last name.

The winding court battle became a staple of local news for at least a couple of years, revealing private details of the heiress’ life and unleashing accusations of abuse, manipulation and unethical behavior on both sides.

Along the way, the court blocked the couple from amending the trust to ensure that the spouse would be left $40 million and all of Kawananakoa’s personal property. The court also nixed an attempt to auction off 400 of the heiress’ personal belongings, including furniture, works of art, silverware and Polynesian artifacts.

In 2018 Probate Court Judge R. Mark Browning ruled that Kawananakoa was not mentally capable of changing or revoking her trust or of firing and replacing its trustee.

Two years later Circuit Court Judge James Ashford ruled that Kawananakoa was mentally unfit to handle her own financial affairs. Former Hawaiian Electric executive Robbie Alm was appointed as conservator overseeing the woman’s personal finances.

The dispute continues in court even after her death, as the issue of who will be successor trustee replacing Wright has yet to be settled, among other things.