Sennett was born as Alice Maud Mary Sparagnapane in London to a family who owned a Christmas cracker and confectionery business.

[3] In 1906, Sennett read an article by Millicent Fawcett and this led to her to join the London Society for Women's Suffrage,[4] which helped organise the 'mud march' of February 1907, and her company provided 7,000 red and white rosettes.

[6] Sennett hosted events for the cause and wrote to the press that her opinion and desire not to condemn militancy in the campaign for women's right to vote must be published as prominently as a letter about one debate from suffragist leader Millicent Fawcett.

[3] She also wrote correcting a press report of an incident when she had spoken up in a meeting in Leamington against the Anti-Suffrage League President Lady Jersey.

Sennett strongly condemned force-feeding of hunger-striking suffragettes, including Ada Wright, and was writing to the Daily Herald that it was ' so revolting as to make one ashamed of one's nationality.

[8] Sennett was assisted with the welcome by the National Political League started by Mary Adelaide Broadhurst and Margaret Milne Farquharson.

[10] In 1910, Sennet led a deputation to Downing Street to address Asquith & Lloyd-George,[3] which resulted in the 'Black Friday' incidents of police violence against the women protestors.

And in 1911, Sennett broke windows of the offices of the Daily Mail for not reporting a WSPU rally, her imprisonment was a few days (the newspaper editor paid her fine).

When her sister, Florence, died in 1949 she had carved on her gravestone, as requested "Originator and leader of the women's suffrage march from Edinburgh to London 1912".