She and her sister Gwendoline Elizabeth Davies (1882-1951) were collectors, who inherited their wealth from their grandfather, the industrialist David Davies.
They established an art centre at Gregynog. They started the Gregynog Press in 1922 and the Gregynog Music Festival in 1933. In 1960, years after her sister's death, Margaret Davies donated Gregynog to the University of Wales for use as an arts centre.
They collected mainly Impressionist and 20th-century art. They bequeathed their huge and important collection, including Whistler's Nocturne: Blue and Gold - St Mark's, Venice y213 to what is now the National Museum Wales.
'Davies Sisters Collection', National Museum Wales website. 'Margaret Davies', Wikipedia. 'The Davies Family of Llandinam', Llandinam Lives, website. 'Margaret Sidney davies', ArtUK website.