Mary Abbott, an abstract expressionist of the 1940s and ’50s whose energetic, brightly colored paintings influenced artists such as Willem de Kooning, even as critics and galleries focused primarily on her male peers, died Aug. 23 at a hospice center in Quiogue, N.Y. She was 98 and one of the last links to a generation that upended international art.

Her death, after being treated for a leg infection, was announced by McCormick Gallery in Chicago, which had represented her since 2002. Facing short-term memory loss in recent years, she had “lived in this great envelope of the moment,” said gallery owner Tom McCormick, but continued unabated.

“If you’re an artist you make art,” Ms. Abbott often said, explaining why she continued to work with paints, charcoals and oil crayons at her home in Southampton, N.Y. “Every day you have to go into the studio and work.”

Raised in a prominent Manhattan family, Ms. Abbott traced her ancestry to John Adams and visited the White House as a girl, once running headlong into President Franklin D. Roosevelt. “I wasn’t behaving very becomingly in those days,” she said. By then she was drawing in earnest, following a passion that developed while she recovered from a childhood infection.

Ms. Abbott achieved early renown as a model, appearing on the cover of Vogue and Harper’s Bazaar, but spurned her glamorous upbringing to move into a cold-water flat in the East Village in 1946. Immersing herself in the neighborhood’s burgeoning avant-garde art scene, she befriended artist David Hare, studied under Mark Rothko and Barnett Newman, experimented with peyote while filling the canvas with vivid reds and greens, and discussed painting with Jackson Pollock over drinks at the Cedar Street Tavern.

Years later, she recalled that the master painter had once assaulted her before she managed to fight him off. “I hated Pollock,” she said, according to Mary Gabriel’s book “Ninth Street Women.” “His way of making friends was to knock you down and get on top of you.”

Ms. Abbott found a better friend (and sometime lover) in de Kooning, to whom she dedicated “Bill’s Painting,” an early-1950s work that featured broad brushstrokes of red, pink and orange. According to a biography by Mark Stevens and Annalyn Swan, de Kooning brought kerosene to warm Ms. Abbott’s unheated 10th Street studio, taught her how to attain the right viscosity of paint, and advised her that “an artist is like a homespun philosopher.”

“She told me once that he was the love of her life, and he asked her twice to marry him,” McCormick said. “She turned him down because it would have been the end of her career as a painter. He was too much of a handful.” Nonetheless, the two artists maintained a friendship for decades, with Ms. Abbott frequently visiting de Kooning’s home in Springs, on the East End of Long Island.

Ms. Abbott had found refuge in that area since childhood, when she summered at her grandmother’s home in Southampton. Her work frequently drew on nature, including the changing light off the coast and the lush forests and hillsides of the Caribbean.

“While we often think of abstract expressionism in terms of bravado, I think that Mary Abbott’s paintings were more about emotional gesture, about her inner response to the world,” said Gwen Chanzit, a curator at the Denver Art Museum. In a 2016 video interview, Ms. Abbott recalled that “trying to do things representationally didn’t work for me.” Instead, she said, she found that could “talk” through abstract art.

Ms. Abbott was not a part of the 1951 9th Street Art Exhibition, which helped introduce the world to abstract expressionism, but was exhibited for the next few years at the Stable Gallery in a series of influential shows centered on the New York avant-garde.

She also gained increasing prominence after the 2016 exhibition “Women of Abstract Expressionism,” which Chanzit organized in Denver, bringing together the work of artists including Helen Frankenthaler, Joan Mitchell, Elaine de Kooning, Lee Krasner and Ms. Abbott.

“She was not an aggressive promoter of her work, so her modesty, as well as her sex, worked against her in the competitive environment of postwar contemporary art,” said art historian Helen Harrison, director of the Pollock-Krasner House and Study Center. “To be fair, many of her male contemporaries were also overlooked and underrated, so she was in good company.”

Mary Lee Abbott was born in New York City on July 27, 1921, and raised on Manhattan’s Upper East Side. Her mother, Elizabeth Grinnell, was a poet and syndicated columnist; her father, Henry Livermore Abbott, was a World War I veteran who received the Navy Cross and retired as a captain. They divorced when Mary was young.

She studied at the Art Students League in New York and the Corcoran art school in Washington, and in 1943 married R. Lewis Teague, a painter in the Army and the son of eminent industrial designer Walter Dorwin Teague. They separated within three years, as Ms. Abbott began to focus on her painting.

In the East Village, she studied at the experimental Subjects of the Artist School, where she learned “to draw imagination,” as she put it, and turned fully toward abstract art. Ms. Abbott became one of only a handful of women invited to an artists’ clique known as the Club, where she was assigned to collect membership fees.

“As much as the guys liked to pinch a penny they liked pinching me even more, and I was able to get them to hand over their dues,” she told McCormick in an interview.

In 1949, Ms. Abbott met businessman Tom Clyde; they were both in the U.S. Virgin Islands, formalizing their respective divorces. They married the next year, and his poor health led them to spend winters in Haiti and St. Croix, where Ms. Abbott chased down snakes and worked on her paintings. That marriage ended in divorce as well.

Ms. Abbott taught at the University of Minnesota in the 1970s before returning to New York, where she bought a modest ranch house in Southampton and kept a studio in the SoHo neighborhood of Manhattan. As the neighborhood gentrified, she said she became known as “the crazy art lady on 3,” sullying the building’s buttoned-down reputation before selling about a decade ago.

Survivors include a half sister.

In a 2003 interview with the East Hampton Star, Ms. Abbott recalled that she was 9 when she fell ill with an infection behind her ear, later complicated by pneumonia, that persisted for two bedridden years and marked a break from years spent frolicking outdoors. “As a child, I had been with everything — animals, plants. I didn’t see beauty; I was in it, I was part of it.”

Her infection, she added, launched her into a new relationship with nature and art. “One morning I woke up and looked out the window, at two pine trees that had been named after my brother and I when we were born, Billy and Mary. I realized I wasn’t with beauty and nature anymore; I was seeing it from the outside. So for the rest of my life I’d paint to get with it again.”