Elizabeth (Bessie) Reid Henderson was born at Kaiapoi on 19 November 1873. She was the eighth of nine children of Alice Connolly and her husband, Daniel Henderson, a storeman. A few years after her birth the family moved to Ashburton; by 1883 they were living in Christchurch. Elizabeth attended Christchurch Normal School, then had five years at Christchurch West School. Daniel Henderson died in 1886 and his family struggled financially for several years. Nevertheless, Elizabeth had one term of secondary education, at Christchurch Girls' High School in 1889. One of her elder sisters later wrote that Elizabeth 'was lazy at school and we did not expect great things from her'.
As a young woman, Elizabeth was overshadowed by her talented elder sisters, Christina and Stella. The three were members of a small and 'very select' socialist club, which stimulated Elizabeth's political thinking. By 1899 she had followed her sisters on the committee of the Progressive Liberal Association, a group that had as one of its aims the removal of women's civil and political disabilities. Her first important public role was as secretary to the Canterbury Children's Aid Society, which was concerned with the welfare of neglected and destitute children.
Elizabeth was the first president of the Young People's No License League in 1902, retaining links with the group until 1905, and was a prominent figure in the New Zealand Women's Christian Temperance Union: dominion treasurer (1909–10), national superintendent of its domestic science department in 1913, and Christchurch district president (1913–17). She remained president of the Sumner branch from its inception in 1921 until her death.
On 25 June 1903, at Christchurch, Elizabeth married James McCombs, a draper, whom she had met at the Progressive Liberal Association. They had two children, Terence and Alison (known as Patricia), and raised two orphans. Also in the household were James's mother, Kate McCombs, and Elizabeth's mother and sister Christina. As a member of Parliament from 1913 James was absent when the House was in session but he corresponded frequently with his wife. Once the children were older, Elizabeth spent time with her husband in Wellington.
Elizabeth and James McCombs were committed socialists. They belonged to the Christchurch Socialist Church early in their marriage and later joined the Canterbury Fabian Society, formed in Christchurch in 1908. Elizabeth supported James in his leadership of the Woolston branch of the Social Democratic Party, which he founded in 1913. When he became the first president of the second New Zealand Labour Party in 1916, she was elected a member of the executive.
Elizabeth McCombs became a political figure in her own right in 1921 as the second woman to be elected to the Christchurch City Council. She retained her seat until 1935, when she did not seek re-election. Where other middle-class women had promoted the interests of their sex through women's organisations, she took their cause into the political arena where men were dominant and sometimes obstructed her policies. Her most enduring achievement was the building of the crèche and women's rest rooms in Cathedral Square, the provision of which recognised that suburban women were now using public transport to shop and to seek leisure in the central city.
McCombs was a trail-blazer in her council committee and local-body work. In 1925 she was appointed to the electricity committee, where she fought to win ratepayers the lowest domestic electricity rates in the country. Cheaper power would encourage demand and increase profits, but her goal was to make life easier for the housewife and thus to promote the domestic feminism she had advanced in the WCTU. In 1929 and from 1931 to 1935 she chaired the committee – the first woman to do so. She was adamant that the Municipal Electricity Department should retain control of its substantial reserve funds in order to benefit consumers. Consequently, she considered it immoral to transfer these to other purposes but reluctantly made an exception in 1929 when the council borrowed £12,500 for unemployment and £8,000 for the women's rest rooms in Cathedral Square.
Elizabeth McCombs was involved in many activities beyond her work on the council. She worked to alleviate the suffering of the unemployed as a member of the hospital board's benevolent committee from 1926 to 1934, and from 1933 was also on the committee administering the Mayor's Relief of Distress Fund. As a member of the North Canterbury Hospital Board from 1925 to 1934, she insisted on hygiene and nutritious meals for patients and nurses and campaigned to improve nurses' working conditions. In 1927 she became the first woman and the first Labour representative on the Christchurch Tramway Board. Outnumbered, she was unable to prevent the confrontation that led to the strike of 1932. Her efforts were noted, however, and she was one of only two members of the committee to be re-elected. Recognition for her work came in 1926 when she was one of the first women in New Zealand to be made a justice of the peace.
In 1928 Elizabeth McCombs stood, unsuccessfully, for the parliamentary seat of Kaiapoi. She was the first woman to be endorsed as a candidate by the Labour Party. Elizabeth was conscious that her sex was an obstacle, and in her second attempt to win a seat, at Christchurch North in 1931, she faced the issue squarely by using as her slogan: 'Vote the first Woman to the New Zealand Parliament'; she admitted publicly that this distinction was, indeed, her ambition.
James McCombs died in August 1933 and Labour leaders had reservations about Elizabeth's replacing him because he won with only a slender majority. Women's groups backed her, and although one of her opponents argued that 'the difficulties of the country are too great for women to grapple with', she was elected with an overwhelming majority and took her seat in the House in September 1933.
As a member of the opposition, Elizabeth had little opportunity to effect change. Instead, she exploited the attention she received as New Zealand's first woman MP to publicise her policies. She was a skilled and effective orator, and in her maiden speech, 'speaking in clear, measured tones', she attacked the government's unemployment policy, accusing the ministry of 'mental euthanasia'. She emphasised that women were not included in the unemployment statistics and that they received minimal relief when they were out of work, although women who had jobs paid unemployment taxation. She expressed a similar concern for unemployed youths and urged the government to heed women's demand for the appointment of women police. On other occasions, she advocated equal pay for women, upheld the citizenship rights of women married to men of other nationalities, and promoted the establishment of New Zealand industries as a means of reducing unemployment.
Throughout her life Elizabeth experienced indifferent health and suffered particularly from asthma. Despite failing strength, she continued to commute weekly between her home and Wellington when the House was in session. She died at Christchurch on 7 June 1935, survived by her two children; Terence succeeded to her parliamentary seat. Elizabeth McCombs had dedicated herself to improving the lot of women and had demonstrated that women were the equal of men in political life. She and her husband are commemorated by the McCombs Memorial Garden in Woolston Park.