Born Ellen Wordsworth Crofts in Leeds, the daughter of Ellen née Wordsworth, the daughter of a Leeds industrialist, and John Crofts, a magistrate and worsted and woollen manufacturer,[1] she was a cousin of the utilitarian philosopher and economist Henry Sidgwick.

A close friend from her Newnham days was the British classical scholar and linguist Jane Ellen Harrison.

[6] In the summer of 1888, Ellen Darwin wrote to her sister-in-law, Ida, to say that her friend Amy Levy was intending to pay a visit, confiding: "She has written a novel, in which the heroine is partly me.

Levy's second novel Reuben Sachs: A Sketch was published shortly afterwards and caused some controversy with its satirical description of a well-off Anglo-Jewish community and its depiction of the Victorian marriage market.

Ellen was strongly agnostic and took her discussions seriously, a friend observing "It was at once distracting and delightfully amusing to hear her say, as she not infrequently did, 'I know I’m right'".