Edith Windsor has died.

The senior woman who became the unlikely face of a movement and a lawsuit to champion the right of same-sex couples to marry died Tuesday, September 12, at her home in New York. She was 88. The cause of death was not immediately made known but it was known, even during the litigation of her lawsuit against the Defense of Marriage Act, that she suffered from heart disease.

Known as “Edie” to most, Windsor was 84 when she became an internationally recognized plaintiff in a lawsuit challenging the DOMA.

With the help of attorney Roberta Kaplan and the ACLU’s National LGBT Project, Windsor filed suit in the U.S. District Court for the Southern District of New York to challenge DOMA’s treatment of her following the death of her first spouse, Thea Spyer.

Windsor and Spyer had been together as a couple for 44 years and had obtained a marriage license in Toronto, Canada, in 2007. Spyer died in 2009, following a long illness. But because DOMA prohibited the federal government from recognizing the marriages of same-sex couples, Windsor was not able to claim the estate tax deduction available to the spouses of straight married couples. The disparate treatment cost her $363,053 in federal estate tax on Spyer’s estate.

In one of its most significant LGBT-related rulings ever, the U.S. Supreme Court in June 2013 struck down DOMA. In a 5-4 decision, U.S. v. Windsor, the majority said DOMA violated the Fifth Amendment guarantee that no person shall be “deprived of life, liberty or property without due process of law.”

In an interview with the Wall Street Journal a year later, Associate Justice Ruth Bader Ginsburg said Windsor was “such a well-chosen plaintiff.” While legal groups do often carefully choose their plaintiffs in test case litigation, Windsor self-selected and sought out attorney Roberta Kaplan to file her lawsuit.

In her book Then Comes Marriage, released in 2015, attorney Kaplan revealed that her effort to represent Windsor ran up against the effort of Boston-based Gay & Lesbian Advocates & Defenders (GLAD) to press two of its own cases. Publicly, attorneys for all the DOMA lawsuits maintained a veneer of camaraderie, but Kaplan acknowledged that she felt Windsor’s lawsuit was the target of a press release many national LGBT groups signed onto in 2009, warning that some challenges to DOMA might set back the movement for marriage equality.

“[I]f the major gay rights organizations had had their way, we never would have filed Edie’s lawsuit in the first place,” wrote Kaplan in Then Comes Marriage: United States v. Windsor and the Defeat of DOMA. In fact, the nation’s oldest and best-known LGBT litigation group, Lambda Legal Defense, declined to help Windsor. And the ACLU, which ultimately joined Kaplan, was hesitant at first.

Kaplan said the ACLU worried that Windsor’s image as a “privileged rich lady” was “not a story that’s going to move people.”

And Kaplan acknowledged that even she worried about Windsor’s unembarrassed candor in talking about her personal relationship with Spyer.

“I wanted the judges (and potentially Supreme Court justices) to see Edie and Thea’s relationship for its qualities of commitment and love,” wrote Kaplan, “not for anything having remotely to do with their sex life. It just seemed safer that way.”

But all the major LGBT groups and activists were quick to acknowledge the significance of Windsor’s historic legal victory and her activism.

GLAD called Windsor a “true warrior for love and justice” and said “she helped the nation and the Supreme Court to see the humanity in the relationships of same-sex couples.”

Susan Sommer, director of constitutional litigation for Lambda Legal, said Windsor “fearlessly stood up for herself and her community.”

“She called for the respect and dignity denied to same-sex spouses, and the Supreme Court heard her plea,” said Sommer. “Because of Edie, we are a more perfect union. She left an indelible mark on all who knew her story, and all whose love is now recognized and protected because of the victory she helped secure for LGBT people.”

“Edie was my close friend, supporter and a mentor,” said Quinn, in a statement. “When New Yorkers – especially young LGBTQ New Yorkers – saw Edie on the street, they’d run up to her, thank her, hug her, sometimes with tears of gratitude and tell their stories and detail how her story touched their lives. She’s a civil rights giant who will impact hundreds of thousands of people for decades to come and will be remembered as a woman whose bravery and insistence on equality and respect changed the course of history.”

Kaplan issued a statement, saying, “Representing Edie Windsor was and will always be the greatest honor of my life. She will go down in the history books as a true American hero. With Edie’s passing, I lost not only a treasured client, but a member of my family.… I also know that her memory will be a blessing not only to every LGBT person on this planet, but to all who believe in the concept of b’tzelem elohim, or equal dignity for all.”

The New York Times reported that Windsor re-married last year to Judith Kasen-Windsor, who is her only legal survivor.

Following her victory at the Supreme Court, Windsor became involved in other LGBT campaigns. She endorsed Christine Quinn in her bid to become the first lesbian mayor of the nation’s largest city, served as the grand marshal of New York City’s annual LGBT Pride parade, and came in third place in Time magazine’s “Person of the Year” poll in 2013.

And though Windsor acknowledged having come out only “selectively” for most of her life, she contributed quietly to the LGBT movement prior to her lawsuit, and many media reports referred to her as the “matriach” of the LGBT civil rights movement.

In a posting on Facebook Tuesday evening, former President Barack Obama said he spoke with Windsor just a few days ago.

“Edie spoke up – not for special treatment, but for equal treatment,” wrote Obama, “so that other legally married same-sex couples could enjoy the same federal rights and benefits as anyone else.”

Windsor and Spyer’s relationship was the subject of a touching 2009 documentary, Edie and Thea: A Very Long Engagement, that has won numerous awards. Born Edith Schlain to Jewish immigrants from Russia, she grew up in Philadelphia and first realized she was gay while attending Temple University. In the 1950s, at a time being gay was harshly stigmatized, she married a man and changed her last name to his, Windsor. The marriage was over within a year, and Windsor moved to New York and eventually became immersed in the gay community. She also earned a master’s degree in mathematics at New York University and landed a job working with computers for the U.S. Atomic Energy Commission and, then, as a computer programmer for IBM.

Windsor and Spyer began their relationship in the early 1960s and considered themselves married. Spyer eventually developed multiple sclerosis, and the couple registered as domestic partners when that became possible. As Spyer’s condition worsened, they decided to seek a marriage license in Canada. Spyer died two years later, in 2009.

A public memorial service for Windsor has been scheduled for Friday, September 15, at 12:30 at the Riverside Memorial Chapel. Windsor requested that, in lieu of flowers, any donations in her memory be made to one of the following four LGBT organizations: The LGBT Center of New York, the Callen-Lorde Community Health Center, the Hetrick-Martin Institute for LGBTQ youth, or SAGE (Senior Action in a Gay Environment).