When the modernist writer Virginia Woolf saw A Conversation, a painting by her elder sister Vanessa Bell, she wrote a fan letter. For this nuanced vision of three women talking, Woolf called Bell “a short story writer of great wit,” and admitted to sibling envy for the unusual, even radical, picture. A Conversation is now the centerpiece of “Vanessa Bell: A Pioneer of Modern Art,” opening today at the Courtauld Gallery, in London.

Her sister aside, Bell’s fan club remained limited for a long time. While other members of the Bloomsbury group became stars in their fields—John Maynard Keynes in economics, Lytton Strachey in biography, Duncan Grant in art, and Woolf in literature—Bell is known more as a member of the group, according to Rachel Sloan, curator of the Courtauld exhibition, than as a major artist in her own right.

Bell was inspired by Matisse, Cézanne, and Picasso.

But artistic winds are shifting. This show comes after a large 2017 exhibition at London’s Dulwich Picture Gallery, and an even bigger exhibition is arriving in October at the MK Gallery in Milton Keynes, 50 miles northwest of London.

The Courtauld, meanwhile, shows us what the fuss is about. In the early years of the 20th century, Bell saw the revolution that Matisse, Cézanne, and Picasso were creating in Continental Europe and developed her own English equivalent, without leaning on Bloomsbury colleagues such as Grant and the artist-critic Roger Fry.

Some of her most significant experiments came just before and during the First World War, when she was in her 30s. Bell painted A Conversation in 1913 and then returned to it in 1916. Its three women are monumental, a formal unity, yet the moment is full of action as the speaker inclines toward the others. Are they dishing, discussing serious matters, or both? The speaker’s left hand falls in a relaxed way over her right thigh, while our attention is drawn to her right hand in the middle of the picture, the fingers folded, the back of the hand almost perpendicular to the wrist—a tense and rarely depicted position.

Design for a Folding Screen—Adam and Eve, painted by Bell circa 1913–14.

Bell tosses out perspective and fills the picture with uncertainties. Are the listeners wearing hats, or does their “headgear” belong to the landscape framed by curtains? The things Bell leaves out—while leaving in the fascination of the conversation—summons up Woolf’s later literary experiments: in Jacob’s Room, the title character lives and dies almost entirely through other people’s eyes; and To the Lighthouse consists of two minutely observed days that are divided by a 10-year fast-forward interval of marriages, deaths, and other major plot points.

Bell’s Design for a Folding Screen—Adam and Eve (1913–14) also plays with disappearance. The Biblical couple frolics in paradise, Matisse-like, and as Sloan points out, the snake, apple, and any sense of guilt have gone missing. To Sloan, the design “represents the sexual freedom that Bloomsbury advocated for.” Bell herself had a romance with Fry and a deep relationship with the mostly gay Grant, who fathered her daughter, Angelica. Clive Bell, with whom Vanessa had an open marriage, agreed to raise Angelica as his own.

Grant, Fry, and Bell were business partners in the Omega Workshops, which for six years funneled Bloomsbury ideas into crafts. The Courtauld presents abstract rug designs by Bell, which foreshadow one of her major occupations in decades to come: the decorative arts. But she always emphasized feelings and sensitivity over mere mechanical ability. In a lecture in 1925, she said, “When art is on the downward grade, skill tends to get the upper hand.”

Despite the tragic death of her oldest son, Julian, in the Spanish Civil War, and the early loss of siblings (she outlived Virginia by 20 years), Bell was often serene and sometimes disturbingly detached. Woolf compared her to “a bowl of golden water which brims but never overflows.” All her life, Bell’s favorite writer was that model of balance, Jane Austen.

“Vanessa Bell: A Pioneer of Modern Art” is on view at the Courtauld Gallery, in London, until October 6

Peter Saenger has written and edited for The Wall Street Journal on such topics as art, art books, museums, and travel. His fiction has appeared in The New Yorker