She was a life long champion of De Stijl movement and advisor to notable American art collector, bohemian and socialite Peggy Guggenheim.

During the opening of the La Section d'Or exhibition in The Hague on 11 July 1920, she was completely captivated by this man, and fell in love in what she later called a "coup de foudre".

[4] The following day she played compositions by Vittorio Rieti during a dada evening at Hotel Fürstenhof in Weimar, in which Jean Arp and Tristan Tzara also participated.

Following this tour she played compositions by Arthur Honegger, Daniël Ruyneman, Francis Poulenc, Josef Hauer and Egon Wellesz during a "Modern Soirée" on 12 March at the Lily Green dance school in The Hague.

From 2 October 1929 to 5 January 1930 she organized the ESAC (Expositions Sélectes d'Art Contemporain) of "contemporary young Parisian painting" at the Stedelijk Museum in Amsterdam and Pulchri Studio in The Hague.

She wanted to help change the one-sided image of Theo being primarily a follower of artistic movements instead of an innovator of modern art .

Though they shared a lot of their social circles, in the artistic avant-garde at the time, Peggy and Nelly did not meet in person until 1938 in London after which they developed a close friendship.

She had a short relationship with the German architect Ludwig Mies van der Rohe, who helped her with setting up an exhibition of her late husband's work in Chicago in 1947.

It is rumoured that Nelly van Doesburg had an affair with Jazz musician Thelonious Monk who she met whilst in at the Minton's Playhouse, and continued the relationship in the De Stijl house in Meudon.