Christina Kirk Henderson was born, according to family information, on 15 August 1861 at Emerald Hill, Melbourne, Australia. She was the second of nine children of Alice Connolly and her husband, Daniel Henderson. Her mother had been a governess at the time of her marriage; her father was variously a trader, storekeeper, grocer, flax-miller and clerk as he moved from Victoria to Tasmania, and then, in 1863 or 1864, to Auckland, New Zealand. A brief sojourn in Tauranga in the late 1860s was followed by periods in Kaiapoi and Ashburton before the family finally settled in Christchurch around 1882.
The Henderson children were brought up in an old-fashioned Presbyterian way, 'on porridge and the Shorter Catechism.' They were all voracious readers; Christina possessed an excellent library and always gave presents of books to her nieces and nephews. She attended school in Auckland, Kaiapoi and Ashburton. By December 1878 she was a pupil-teacher at Ashburton School, attending teacher training classes before and after school and on Saturday mornings. She then won a scholarship to complete her training at the Christchurch Normal School. In 1881 she passed the examination for a class D certificate and was briefly relieving headmistress at the Normal School. From 1883 to 1885 she taught at Springston School, at the same time enrolling for part-time study at Canterbury College. She graduated BA from the University of New Zealand in 1891.
Daniel Henderson's death in 1886 left his widow struggling to bring up the youngest members of a large family on a low income. Christina Henderson helped to support the family for many years, a burden which increased when her older sister Alice began work as a missionary in 1896. In 1886 she obtained a position at Christchurch Girls' High School, where she remained until her retirement from teaching in 1912. She became first assistant in 1889 and was acting lady principal for a time in 1898, but apparently the board of governors considered her too radical to be appointed permanently. A highly respected though stern teacher, Henderson taught Latin and English, established the school magazine and was first president of the debating club. An active cyclist and walker (she tramped the Milford Track in 1900), she also assisted with annual sports days.
Her upbringing and straitened circumstances left Christina Henderson with a serious nature, strong religious beliefs and socialist sympathies. Her principles were fostered by her membership of a small socialist club in Christchurch during the 1880s. She saw capitalism as cruel and unjust, especially to 'the weak, disorganised masses' of women workers. Her own position as a female teacher, earning only half the pay of men doing the same job, confirmed her belief in equal pay for equal work. 'It is quite true that a woman manages to live on less than a man because her wants are fewer, but it is equally true that her wants are fewer because her earnings are less', she wrote tartly. Henderson became the first president of the Association of Women Teachers, founded in 1901 to secure a better status and remuneration for women teachers.
She had an abiding concern for the welfare of women and children. In the early 1890s she joined the women's franchise campaign and the Canterbury Liberal Association, and in 1898 the Canterbury Children's Aid Society. To these causes Henderson would bring formidable energy, a clear, logical mind, superb writing and organisational skills, and a vigorous approach based on exhaustive knowledge. Henderson also became a member of the National Council of Women of New Zealand, and was secretary from 1902 to 1905. It was she who maintained contact with the International Council of Women after the New Zealand body foundered, and she was one of three women who were responsible in September 1916 for reviving the organisation. Henderson became secretary again in 1919, but resigned for health reasons in 1922; possibly the conservatism of the new NCW did not appeal to her. She also served as secretary (1917–19) and then president (1919–24) of the Christchurch branch. She fought for the right of women to serve as police, members of Parliament, jurors and justices of the peace; she herself was appointed a justice of the peace on 23 February 1928.
Christina Henderson's deepest enthusiasm was reserved for the prohibition campaign. She was conscious of 'the futility of advocating other reforms, when so few women could be economically independent and when drunkenness brought misery and poverty to so many homes.' An early member of the Christchurch Prohibition League, she was honorary secretary from about 1901 until 1913. In 1912 she edited the Reformer, a prohibition magazine. From that year, freed from all domestic responsibilities except gardening, which she loved, social reform became her life. 'I hope that everyone will think only of the work – the worker doesn't count', she wrote.
Christina Henderson's long association with the Women's Christian Temperance Union of New Zealand began in 1913 when she was elected corresponding secretary and legal and parliamentary superintendent. Until 1938 she was responsible for scrutinising all legislation affecting women and children, a task involving countless letters, petitions, submissions and deputations. Henderson was a strong advocate of work with the young and was also actively involved in patriotic work during the First World War. She was president of the Christchurch branch of the union from 1926 until 1946, and continued to attend meetings until the year of her death.
Alice Henderson's mission work led Christina to take an active role in the Presbyterian Women's Missionary Union of New Zealand. She served as secretary (1917–20) and president (1930–32), but her main contribution was her editorship, from 1923 until 1946, of Harvest Field, the union's magazine. Christina brought 'sympathy and encouragement' to Alice's years of missionary endeavour, visiting her twice and supporting her financially. The two sisters shared a missionary union house at Sumner in the last years of their lives. Christina, whose mind remained clear to the last, died aged 92 in the Public Hospital, Christchurch, on 27 September 1953. She had never married.
Christina Henderson was 'singularly undemonstrative', and often seemed unloving to her family despite her passionate affection for them. She had, however, a keen and subtle sense of humour, and her pungent wit was often interspersed with trenchant sarcasm. 'She gave of her best to any cause that she considered was for the betterment of the community and was not deterred by difficulties', but she expected others to meet her own high standards.