Hermina Arndt (known as Mina) was born on 18 April 1885 at Thurlby Domain, the family property near Arrowtown, New Zealand.  Early in 1907, following the example of artists such as Edith COLLIER, she left for London with her mother and her two sisters. There she attended  art school where her teachers included Frank BRANGWYN. She may have attended classes at the Slade. With German printmaker, Hermann Struck, she studied etching in Berlin, first in 1907, as Arndt had family ties there and spoke German, while many of her compatriots were studying in Paris.  In late 1907 or early 1908 she joined the FORBES SCHOOL in Newlyn, Cornwall. Here, she met the Samuel John Lamorna BIRCH family,  Harold KNIGHT, Laura KNIGHT and others in the NAG circle.  She shared the Newlyn School's interest in depicting peasants, and her portraits of Cornish peasant women from that time echo the Cornish work of  Edith Marion Collier.  

Arndt exhibited  two works at NAG in Newlyn (March 1914) just before the Gallery closed for the duration of WWI [no record]. She was back in Germany by August that year and when WWI was declared she and her sister Edith were briefly interned, then released as part of an exchange of women prisoners. After returning to New Zealand in 1914 Arndt lived in Wellington, renting a studio. In 1915 she exhibited 93 of her European drawings, oils and etchings to mixed reviews.  She married Lionel Manoy, a widower, in a Jewish ceremony in Wellington (1917). They had one son, John. 

In 1924 she was awarded a medal at the British Empire Exhibition, Wembley. Following her death, Arndt was largely ignored until the 1960s when her place in New Zealand art gained further recognition. In 1960 her son and stepdaughter initiated a retrospective exhibition at the Bishop Suter Art Gallery in Nelson, and in 1961 the New Zealand Academy of Fine Arts held a retrospective exhibition in Wellington. Since then an interest in women artists and the development of modernism in New Zealand art have contributed to an increased awareness and appreciation of her art. Her work is represented in private collections and galleries in New Zealand, and in galleries in England, Australia and France.