Eethel Horsfall was born in Lancaster. It was as an art student in Paris that she met her husband, Edward ERTZ, at that time Professor of Watercolour at the Delecluse Academy. After their marriage the couple moved to Polperro, where they set up their first painting school.

Polperro was the birthplace of their two children. Both husband and wife exhibited from there and at the RA. 

By 1905 the family had moved to Devon, where they set up a painting school in Yealmpton, and later one near Kingsbridge. This was followed by a move to Pulborough in Sussex. On her premature death from a stroke in 1919, she was described as 'a watercolour painter of rare technical ability and poetic feeling and was best known by her vibrating moonlight pictures at the Royal Academy'.