Complex sentence: She studied at Sydney Art School from 1896 under Julian Ashton then St John's Wood School in London in 1903; they became lifelong friends and she modelled for him many times.
Split into simpler sentences: She studied at Sydney Art School from 1896 under Julian Ashton, then at St John's Wood School in London in 1903. Ashton and Proctor became lifelong friends and she modelled for him many times.