The younger sister of the statesman Richard Burdon Haldane and the physiologist John Scott Haldane, she was educated privately. For much of her adult life she served on various advisory and regulatory boards for nursing. Influenced by the English housing reformer Octavia Hill, Haldane founded in Edinburgh (1884) an organization for slum reconstruction and housing-project management. She was the first female (from 1914) of Andrew Carnegie's United Kingdom Trust, which she induced to rescue the Sadler's Wells Theatre and Ballet (London) from penury. In addition, she was the first woman to be justice of the peace in Scotland (appointed 1920).

Haldane translated philosophical works by G.W.F. Hegel and René Descartes and wrote several biographies, as well as The British Nurse in Peace and War (1923) and a volume of reminiscences, From One Century to Another (1937).