After attending Alcester Grammar School, she studied at the University of Wales, Aberystwyth, graduating in 1922 with a Bachelor of Arts degree in history.
She then worked for Political and Economic Planning, before joining the University of Nottingham in 1950 to oversee research projects, one of which examined youth groups and was published as Some Young People (1954).
That year she became a senior research assistant at the London School of Economics, working under Richard Titmuss alongside Nancy Seear and John Smith.
[1] In the view of Helen McCarthy, this study meant that Jephcott was one of a number of researchers in the 1950s and early 1960s (such as Seear, Viola Klein, Ferdynand Zweig, Judith Hubback and Hannah Gavron) who "helped to entrench new understandings of married women’s employment as a fundamental feature of advanced industrial societies, and one that solved the dilemmas of 'modern' woman across social classes.
[3] Professor John Goodwin, University of Leicester, a champion of Jephcott's innovative and creative work,[4] contributed introductory essays to each volume.