Muriel was born about 1889. She is the daughter of William Hall and Ida Keeton and is mentioned in her fathers death notice of 1935.
FamilySearch: "South Africa, Cape Province, Kimberley, Probate Records of the Supreme Court, 1871-1937." Database with images. FamilySearch. http://FamilySearch.org : 24 January 2018. National Archives of South Africa, Cape Town Archives Repository, Cape Town. (Death Notice of father William Herbert Hall.)