She was born in Marsden, close to Huddersfield, Yorkshire, Great Britain. In 1890 her father abandoned the family after economic failures at his textile plant. She began working as a tutor at the age of thirteen. At the age of eighteen she attended the University of Manchester for three years, then worked full-time as a teacher for five years. Marsden became involved with women's suffrage during her studies. In 1909 she was arrested for her political activity and subsequently accepted a full-time position with the Women's Social and Political Union, only to leave it in 1911 due to conflicts with its leadership.
Her most important cultural contribution was the editing of three publications, the latter more or less continuations of the previous series, beginning in late 1911:
The magazines were mainly published under the patronage of author Harriet Shaw Weaver. During the course of publication the political bias of Marsdens editorials tackled subjects related mainly to feminism. Though she also commented on egoism and individualist anarchism, her quarrels with Benjamin Tucker ended with her rejection of Tuckerian anarchism and an embrace of "archism".
Literally, the publications were high-standing, propelling the modernist movement. Ezra Pound, T. S. Eliot, D. H. Lawrence, Wyndham Lewis, Herbert Read and James Joyce contributed material to the periodical. Joyce's Portrait of the Artist as a Young Man was published for the first time as a series in The Egoist.
The Egoist (a name suggested by Ezra Pound) was not named in the honour of the philosophical egoist Max Stirner. Rather, it was a philosophical term that was "in the air" by the time, associated with writers such as Friedrich Nietzsche and Maurice Barrès. When Stirners book The Ego and Its Own was published, Marsden never fully reviewed it; she did admit to liking it but also partly dismissed it, mostly on the ground that she disagreed with Stirner about the nature of God: Stirner saw God as a repressive idea, imposed from the outside, from society, so it could control the individual. Alternatively, Marsden claimed that god was an invention of the self in its attempt to encompass the world and rule over it, hence, a positive, freeing idea.
In 1920 Marsden withdrew from the literary and political scene and spent fifteen years in seclusion, completing a "magnum opus" drawing from philosophy, mathematics, physics, biology and theology. It was eventually published by Harriet Shaw Weaver in two volumes as The Definition of the Godhead in 1928 and Mysteries of Christianity in 1930.
This large body of work produced by Marsden was not well received (not even by her former supporters) and she suffered a psychological breakdown in 1930, which was further deepened by the death of her mother in 1935. As a result, she spent the last 25 years of her life in a home for the psychologically ill in Dumfries, Scotland.