I have come across Miss Violet Mount in doing some research on Trove, a wonderful, Australian, newspaper database. She was slightly associated with my subject, an Australian violinist, and they were both in England before the war. Though there hasn't been much biographical work done on Violet Emily Le Breton Mount, there is plenty in the papers, at least, so I've made a start on some lists on Trove, here (under "Lists"):
Violet Mount.
In brief, she was born in Caulfield, a suburb of Melbourne, Victoria, Australia, on 15 March, 1875. Her father, Lambton Le Breton Mount, was quite a character. He had been brought to Ballarat, Victoria, from Canada, by his father, apparently for the gold rush in the 1860's. He went on to do a spot of pioneering in West Australia, sheep farming. His partner in that enterprise was
Adam Lindsay Gordon, a noted Australian poet. Back in Melbourne, he ran a bottle-making works and started his family. But he sold up and took the family to Europe in 1893. Violet had already begun singing publicly with a choral society in Melbourne and she had the opportunity to further her training in Europe. Back in Melbourne a few years later, she continued her training with the Howard Conservatoire of music and began performing in 1897.
Apparently already having decided on a professional career, she moved to Wellington, New Zealand, in 1899 and worked there until 1901. She moved to Auckland (the larger city there) and again worked her way up through the ranks. Before moving to Sydney, Australia, in 1902, she had a success in the title role of Schumann's "Paradise and the Peri".
In Sydney, she worked with Signor Roberto Hazon, an Italian conductor who did much for developing musical culture in Sydney in the 1890s and 1910s. After working in both New Zealand and Melbourne again, from 1905 to 1907, she left for England in mid-1907 with her mother, who was also a singer. In London, however, she could not find work until she made the shift to vaudeville, singing a selection of her opera repertoire; and, with the gimmick of the mask, the name "L'Incognita" and, no doubt, rumours spread by her agent (that she was some high-born runaway and so forth), she became an instant success at The Alhambra in March, 1908. A recording contract swiftly followed, hence your records. She was for several years the most successful Australian, at least, working in the UK. But she never, so far as I have found, worked in real opera in Europe, as was, no doubt, her original ambition.
Her career revived in the early 1920's and I have an article noting that she was living in Hampstead with her then 90-year-old father in 1926. (Apparently, the singers lived in Hampstead as it was high and out of the London smog.) She was, apparently, still in England in 1936 but I lose track of her then so I can't help you with when or where she died. Though she still had family in Australia, I imagine that she stayed on in England, however.