Harriet, her sister, and her mother first came to Canada from England in 1851, after Mrs. Mills accepted a teaching position in the Red River Colony.

The young ladies were trained in all the social etiquette of the day in addition to the more solid education imparted.

Miss Harriet Mills (the younger daughter) was more of a companion to the girls, and accompanied them on walks, in winter on the frozen river, in summer towards the plain.

[6] On 11 March 1858, Miss Harriet Mills (the younger daughter) married Alfred Robert Roche[1] (1819–1876)[7] in Staplegrove, England, one of the parishes of Taunton, in Somerset.

[8][1] Harriet's book, On Trek in the Transvaal; or, Over Berg and Veldt in South Africa was published in London by Sampson Low, Marston, Searle & Rivington, in 1878.

[1] Boomer was born in Ireland, and educated at the Royal Belfast Academical Institution, and at Trinity College, Dublin, having graduated from the latter in 1838, and there receiving the honorary degree of Doctor of Laws, in 1860.

[11] Harriet's second book, Notes From Our Log in South Africa; and, On Foot Through the Colonies at the Paris Exhibition, was published in London, Ontario by the Free Press Printing Company, 1880.

[11] During the remainder of her life, Harriet Boomer performed volunteer work associated with the Church of England and was an active public speaker.

She served as a member of the school board of London, Ontario, where she lived, and as president of the Toronto Local Council of Women (TLCW) circa 1900.

[2] She was regarded by Ishbel Hamilton-Gordon, Marchioness of Aberdeen and Temair as a personal friend and "a great feature in our National Council, for her tact & sense of humour has helped us over many a rough place.

[8] At some point after Dean Boomer's death, she published Little Miss Ellerby and her big elephants: respectfully dedicated to all whom it may concern, a juvenile "dream" that is really about reducing parish debt.