Unlike most portrait painters featured here, Helleu seldom worked in oils. He preferred pastel and etchings. Judging by images of his works found via Google and Bing searches, his heyday seems to have been 1895-1915 or thereabouts.
Some of the images below strike me as being rather conventional, a contemporary Gallic variation on stereotypical Gibson Girls. Others are more interesting, better evoking the personality of the sitter.
Helleu married her.
One of the famous sisters.