Born in Montreal, she grew up in Belleville, Ontario, Canada. A great-granddaughter of Nahum Mower of the Kingston Gazette, she enjoyed inherited wealth which supported her until the 1940s. She studied at the The Royal Conservatory of Music (then the Toronto Conservatory). She travelled extensively in Europe and Egypt as a young woman, spending a few months in England in 1907. She returned to Canada, then moved to London permanently about 1912.
At the beginning of the 20th century, the British suffragette movement, frustrated by a failure to achieve equal voting rights for women, began adopting increasingly militant tactics. In particular, the Women's Social and Political Union (WSPU), led by Emmeline Pankhurst, frequently endorsed the use of property destruction to bring attention to the issue of women's suffrage.
Richardson was a member of the WSPU, and a devoted supporter of Mrs Pankhurst. She smashed windows at the Home Office and burned down The Elms, a historic mansion in Hampton, with her accomplice, Jane Short. She also committed the most sensational deed of the militant campaign: slashing the Rokeby Venus, a priceless painting. She was arrested nine times, receiving prison terms totalling more than three years.
She was one of the first two women force-fed for hunger-striking, then released to recover and be re-arrested under the 1913 Cat and Mouse Act, Prisoners (Temporary Discharge for Ill Health) Act 1913, serving her sentences in HM Prison Holloway. Richardson was given the Hunger Strike Medal 'for Valour' by WSPU, and was proud of being awarded more bars for strikes than anyone else.
After one of her many hunger strikes Richardson recovered at the cottage of Lillian Dove-Willcox in the Wye valley. She was devoted to Dove-Willcox and wrote the poem The Translation of the Love I Bear Lillian Dove.
On 10 March 1914 Richardson entered the National Gallery in London to attack a painting by Velázquez, the Rokeby Venus, using a chopper she smuggled into the gallery. She wrote a brief statement explaining her actions to the WSPU which was published by the press:
The canvas was later fully restored.
Richardson was on the far Left, anti-war and a committed Christian.
During the First World War she worked with Sylvia Pankhurst in the East End and joined the Labour Party about 1918. She later joined the ILP. In the 1920s she stood as a Labour candidate three times. She described herself as "Red, not pink".
In 1933, after unsuccessful attempts to secure a winnable constituency with the Labour Party, Richardson transferred to the New Party, which was anti-war, socialist, and promoted equal opportunities for women. The party was led by Sir Oswald Mosley, who, along with his wife, had recently been Labour MPs. The New Party later became the British Union of Fascists.
Richardson joined in an administrative role as assistant to Lady Makgil, the organising secretary of the women's section within the London headquarters, which was headed by Maud Mosley. When Lady Makgil was suspended for "financial irregularities," Richardson assumed her responsibilities. She trained female members in public speaking and addressed several meetings in smaller venues. In July 1934, she was appointed propaganda officer in the women's section, a role she shared with Marjorie Aitken.
Increasingly dismayed at the BUF's policy of keeping women in subordinate positions, paying them less, and restricting their participation in rallies or office, Richardson called a meeting of female members at her Chelsea flat. Mosley subsequently expelled her. Her involvement was brief, and her departure was not noted in the BUF newsletter.
From 1934 until the end of her life, Richardson was active in socialist organisations.
In the 1950s she attempted to start her own religion, called Redeemism, which called for world peace.
Richardson published two novels, The Greater Waterloo (1905) andMatilda and Marcus (1915), and three volumes of poetry, Symbol Songs (1916), Wilderness Love Songs (1917), and Cornish Headlands (1920). She also wrote a few articles for suffrage publications. Contrary to her claims, she never worked as a journalist or an artist.
Richardson was a lesbian. All her love poems are about women.
In 1930 she unoffficially adopted a baby named Roger, who took her surname. A devoted mother, she took him to rural Cambridgeshire. In 1955, at the age of 73, she moved into a tiny flat in Hastings, East Sussex.
Richardson published an autobiographical work, ', in 1953. It is a collection of anecdotes from her highly eventful year as a suffragette 1913-1914. According to her biographer, none of the anecdotes is entirely true and some are entirely fictitious.
Some of the events at which she is widely reported as being present, or committing, have been demonstrated to be untrue, for example her Epsom Derby story, and her anecdote about bombing a railway station.
She died at her flat in St James's Road, Hastings on 7 November 1961. She was cremated and Roger took her ashes to his London home.