The reference is to Octavia Hill, the social reformer. Ruskin met her when in her late teens she studied drawing under him. In 1864 she and Ruskin embarked on a project to improve housing conditions for the poor in London. They began with six dwellings in Marylebone, which Ruskin had inherited from his father. The experiment met with some success; as W. G. Collingwood puts it,
'They showed what a wise and kind landlord could do by caring for tenants, by giving them inhabitable dwellings, recreation ground, and fixity of tenure, and requiring in return a reasonable and moderate rent' [ The Life and Work of John Ruskin ].