Her sister Beatrice (also called 'Beatrix' or 'Trixie') married James McNeill Whistler in 1888, following the death of her first husband Edward William Godwin.

Ethel married Charles Whibley in 1896 in the garden of the house occupied by James Abbott McNeill Whistler at n° 110 Rue du Bac, Paris.

Whistler painted a number of full-length portraits of Ethel, including Mother of Pearl and Silver: The Andalusian[4] and the watercolour Rose and Silver: Portrait of Mrs Whibley;[5] and other sketches and etchings of her titled as Miss Ethel Philip or Mrs Whibley.

[6][7] Correspondence between family members addressed personal, social and professional matters as Whistler's sisters-in-law acted as his models and secretaries to manage his business affairs.

In correspondence Beatrice Whistler was referred to a 'Trixie' or 'Chinkie'; his sister-in-law and secretary (1890–94) Ethel Whibley was 'Bunnie'; his brother-in-law Charles Whibley was 'Wobbles'; his sister-in-law and secretary Rosalind Birnie Philip was referred to as the 'Major'; with Whistler signing family correspondence as the 'General' when he did not sign with his butterfly signature.