Caroline Sarah Howard, known as Sally, was born at Loburn, Canterbury, New Zealand, on 23 March 1876, the fifth of six daughters of Charlotte Thompson and her husband, Charles Smith Howard, a teacher. Sally attended the schools at which her father taught at Woodend and Richmond. She came from a background where books and education were highly valued, and where progressive views were debated. The Wesleyan Methodist church was a strong influence throughout her life, although not all its members were as liberal as the Howard family. Sally's father, a local preacher, once addressed a neighbouring rural congregation on the subject of the motherhood of God, so upsetting his hearers that they asked that he no longer be rostered to their pulpit.
Sally Howard showed early signs of academic ability. Scholarships took her in 1888 to Christchurch Girls' High School, then headed by Helen Macmillan Brown (née Connon), and in 1894 to Canterbury College. There she gained her MA with honours in 1898, joining the small number of early women graduates. After teaching for a short time in her father's school at Richmond, she was appointed in 1902 as sole assistant to T. R. (Dick) Cresswell, her second cousin, at Rangiora High School, a co-educational rural school. They formed a strong imaginative team, introducing into the syllabus a range of practical subjects. J. E. Strachan later built on this initiative. When Cresswell was ill for some time in 1906 Sally Howard took charge with the help of an assistant, to the evident satisfaction of the school's board.
While at high school Sally had become a close friend of Elsie Low (later Dohrmann), and when they were both at university Sally met Elsie's only brother, Benjamin Harris Low, who was completing his BA. Ben and Sally were engaged in 1896, but a long separation when Ben was teaching in Auckland and Thames caused the engagement to be broken off. Ben married while at Thames, but in 1903 his wife died of tuberculosis six months after the birth of a daughter. In 1906 friends conspired to bring Ben and Sally together again, and on 27 December 1907 they were married at Wesley Church, Timaru. Their family eventually consisted of four sons, and the daughter from Ben's first marriage.
Sally Low retired from teaching and set up house in Wellington, where her husband taught at the Newtown District High School. In 1913 Ben moved back into primary teaching as headmaster of Blenheim School and the side school at Redwoodtown, and in 1919 he was appointed head of the prestigious Timaru Main School. The big schoolhouse, one of the most substantial headmaster's residences in the country, became a centre of support and hospitality to a wide range of visitors.
In the early years of her marriage, Sally Low was a member of Methodist women's groups and local branches of the New Zealand Women's Christian Temperance Union, and through those organisations she maintained and developed her interest in education and social reform. From 1908 to 1913 she was associate editor of the White Ribbon and from 1908 to 1911 was New Zealand superintendent of the Legal and Parliamentary Department of the WCTU.
After the family moved to Timaru she expanded the range of her activities. She helped set up the local branch of the Workers' Educational Association of New Zealand and the British Drama League. Keenly aware of the educational and social value of drama, she participated in WEA play readings and in British Drama League play festivals, both as actor and producer. She was also elected to the Timaru High Schools Board. During her term she is said to have been particularly influential in redressing the inferior status accorded to girls' secondary education.
Possibly Low's most significant undertaking at this time was her advocacy of peace and disarmament. In 1924 she joined the League of Nations Union of New Zealand and in 1928 was appointed dominion superintendent of the Peace and Arbitration Department of the WCTU. Subsequently she addressed many church and women's groups on the desirability of reforming international relations, and on the central role of the league in promoting this end. She soon acquired a reputation as a well-informed and compelling speaker. It was later said of her, 'She imparted a vividness and forcefulness to her addresses, and the sincerity of her appeals commanded the admiration and interest of all sections of the community.' She wrote the peace and arbitration column in the White Ribbon and read a long paper on disarmament to the 1932 WCTU conference.
After Ben Low retired in 1928 he and Sally moved to a smaller house and continued to take part in sporting and community activities. Sally had played good tennis until she was 50 and then turned to croquet and golf. She died on 10 August 1934 at Timaru, aged 58, as the result of a staphylococcal throat infection for which no effective treatment was then available. She was survived by her husband and children.