Bertha Green trained as a painter at private painting schools in the 1890s at, among others Georg Seligmann (1866–1924), Peter Ilsted (1861–1933) and Harald Slott-Møller (1864–1937). Then, like many of the other female painters at her time, she went abroad to further her education. She spent a year in Berlin, where she learned to engrave at the Schinkel Academy and made her debut under her maiden name Green at the Free Exhibition (Den Frie Udstilling) in 1899.

In 1900, she married the painter Niels Vinding Dorph (1862–1931) and was henceforth known as Bertha Dorph. She continued her education both at home and in Italy, France and England. In 1916 Bertha Dorph became a co-founder of, and sat on the board of The Danish Women's Artist association (Kvindelige Kunstneres Samfund). In 1928 she became chairman of The School of Drawing and Art Industry for Women (Tegne- og Kunstindustriskolen for Kvinder), which had been established in 1875.