What Happened to Millie Warne?

According to a brief reference in Beatrix Potter: Writing in Code by M. Daphne Kutzer, Beatrix Potter "remained close" to Millie Warne and other members of the Warne family, despite Harold Warne's arrest for forgery in 1917 or so. I don't know what exactly happened to Millie Warne, but somehow it comforts me to think that she remained friends with Beatrix Potter.