Born into a wealthy and prominent New Jersey family, Frelinghuysen simultaneously cultivated two artistic gifts. A significant figure in the group of American artists devoted to abstraction in the years before World War II, from 1947 to 1951, she was a critically acclaimed featured performer with the New York City Opera. Nonetheless, Frelinghuysen is comparatively obscure today. This is partly a consequence of the irony that well-to-do artists have the luxury of refraining from actively promoting their careers. In Frelinghuysen's case, there are also class and gender-related issues. The product of a socially and economically privileged upbringing in a family whose male members had for generations distinguished themselves in public affairs and business, Frelinghuysen grew up in a milieu that did not encourage women to step forward.
Estelle Condit Frelinghuysen was born in Newark, New Jersey. Her first American forebear, Reverend John Frelinghuysen, emigrated from Holland to the colony of New Jersey in 1720. Reverend Frelinghuysen's son, Frederick, served as a delegate to the Continental Congress, while Frederick's son, Theodore, was attorney General of the State of New Jersey, a United States Senator, Mayor of Newark, Chancellor of the University of New York (now New York University), Whig Vice Presidential candidate in Henry Clay's presidential bid of 1844, and President of Rutgers College. Theodore's nephew (and adopted son), Frederick, was a banker, railroad executive, and a member of the United States House of Representatives and Senate before he was appointed Secretary of State by President Chester Arthur. Frederick's son, also Frederick, was Suzy Frelinghuysen's father. He pursued a private and prosperous life as a lawyer, banker, and insurance company director. His wife, Estelle Burnet Kinney, was the daughter of the publisher of The Newark Advertiser, Newark's oldest daily newspaper. The family, with four sons and a daughter, lived in quiet opulence on an estate in Elberon, New Jersey. Though Frelinghuysen's given name was Estelle (like her mother), she always called herself "Suzy," the childhood nickname given to her by her older brothers. Frelinghuysen's mother was an accomplished pianist and the children received sustained exposure to art and music in Europe and America. As a child, Suzy Frelinghuysen studied voice, and nurtured an ambition to become a professional singer. She also showed a talent for art, but it was not her primary interest. When the family traveled to Europe, they not only visited important art museums, but spent time, as well, at the Bayreuth Festival, dedicated to the perpetuation of the music and legacy of Richard Wagner.
In 1935, Frelinghuysen married George L. K. Morris (1905–1975), a suitable match in every respect. Morris, the Yale-educated scion of a pedigreed, distinguished, and wealthy New York family, was, at the time of their marriage, already an art collector, an abstract artist, and, as a critic, one of the most active proponents of abstract art in America. For Frelinghuysen, the marriage sparked a renewed interest in painting. She found herself in the center of an active, affluent, and socially well-connected group of abstract artists presided over by the artist and collector, Albert Eugene Gallatin (1881–1952). Gallatin was George Morris's tutor, mentor, colleague, distant relation, and friend. He was also the proprietor of a small but influential public gallery founded in 1927 as the Gallery of Living Art, renamed, in 1936, the Museum of Living Art, where he displayed his personal collection of abstract art, as well as small, carefully curated exhibitions of contemporary art by American artists working in the abstract idiom. Gallatin's enterprise occupied a space on Washington Square East, in a New York University building made available to him by the University, of which his great-grandfather, Albert Gallatin was among the founders and he himself was a trustee.
By 1937, only two years after her marriage and her serious return to painting, Frelinghuysen was exhibiting alongside Morris, Gallatin, and their friend, Charles Shaw, at the Reinhardt Gallery in New York. In April of that year she was elected a member of the American Abstract Artists (AAA), of which her husband was a founder. Frelinghuysen, Morris, Gallatin, and Shaw became known colloquially as the "Park Avenue Cubists," a reference to their social register families, their comfortable fortunes and their preferred mode of painting. The group was committed to an American expression of the Cubist style pioneered by Pablo Picasso and George Braque, arguing that abstraction could be as "American" as the popularly prevailing school of regionalist realist artists. Gallatin, in particular, positioned himself as a champion of American artists in contrast to the emphasis on European modernists embraced by Alfred Barr at the Museum of Modern Art, founded in 1929.
In her own work, Frelinghuysen assimilated ideas and stylistic motifs from the work of Picasso and Braque, from her own private collection of art, and from the example of her fellow members of American Associated Artists. She exhibited frequently with the AAA, contributing works to nearly all their annual exhibitions, as well as at Gallatin's "museum." In 1942, NYU abruptly informed Gallatin that they needed to reclaim the gallery space. Stung, Gallatin arranged to remove his collection, including Picasso's Three Musicians, and loan it to the Philadelphia Museum of Art, where it remains today according to the terms of his 1952 bequest. All the while Frelinghuysen worked as a painter, she continued her interest in music performance. In October 1947, she made her debut with the New York City Opera, singing the leading soprano role in Richard Strauss's Ariana auf Naxos. Performing under her married name, Suzy Morris, she received a coveted "rave review" from "H[oward] T[aubman], the music critic of the New York Times:
Miss Morris proved to be the owner of a sumptuous dramatic soprano. Voices of this caliber are said to be almost non-existent in this country, but here was a singer who produced tones of opulence, power, wide range and who used them with mature, musical effect. . . . [With] experience, she could be a prima donna worthy of any opera house. (October 19, 1947, p. 32)
Morris's opera career continued successfully until a bout of bronchitis interrupted it in 1951. Public performance had always proven traumatic for Suzy Morris, and she never returned to the professional stage. As Suzy Frelinghuysen, however, she continued to paint until her death, showing her work at group exhibitions, but never seeking a high profile solo career.
By the time Frelinghuysen returned to concentrate her effort on painting in the 1950s, American abstract art rooted in Cubism had been supplanted by Abstract Expressionism, buttressed by a cadre of influential critics led by Clement Greenberg. Over the next three decades, Frelinghuysen's work slowly began to incorporate some of the expressive and gestural forms of Abstract Expressionism, accelerating after the death of her husband, George Morris, in 1975. The late body of work is perhaps the most underappreciated component of her oeuvre, mostly because these paintings remained in the artist's possession, almost completely unseen, until after her death in 1988.