She often acted as an advocate for K'gari (Fraser Island) and Butchulla issues, and illustrated The Legends of Moonie Jarl, the first known Australian Aboriginal–written children's book to be published.
Her parents' relationship, that of an Indigenous man and a white woman, was deeply controversial in its time and opposed by Ethel's brother Ernest Gribble in particular.
Miller worked in various media, writing for school textbooks, animated films and newspapers; presenting on radio; and illustrating children's stories.
In 1964, she illustrated The Legends of Moonie Jarl, written by her brother Wilf Reeves, which is the first known published children's book authored by an Aboriginal Australian.
[8] In April 2003, she was awarded an honorary fellowship by the University of Southern Queensland (USQ), on whose Fraser Coast campus she had helped establish Buallum Jarl-Bah, a centre for Indigenous learning.