1939 Register has
SHEPHERD Ada H, widowed, born 14 Jan 1887, 28 Belfort Place, Great Yarmouth, Laundry Worker Iron.
Ada Hannah Shepherd on the 1920/1930 Electoral roll at 28 Belfort Place (with Ellen CORKE) must be Ada living there in 1939 (unless it was her mum and "our" Ada moved in and mum moved out or died - unlikely!)
Ada was not with a husband in 1920, 1930 and 1939. Where was he? Who was he? Was he?
If we go with the idea that Ada was the daughter of Charles & Ellenor/Eleanor CORKE, Ada's stated age is a good fit with the 1939 Register:
1901 census: North Quay, Yarmouth
Charles Cork, Head, 50, born St Faiths, Norfolk
Eleanor Cork, Wife, 51, born Gt Yarmouth, Norfolk
Alice George, Daughter, 24, born Ludham, Norfolk
Henry Cork, 19, born Gt Yarmouth, Norfolk
Ada Cork, Daughter, 17, born Gt Yarmouth, Norfolk
George Cork, Son, 15, born Gt Yarmouth, Norfolk
Bertie Cork, Son, 12, born Gt Yarmouth, Norfolk
Victor Cork, Son, 9, born Gt Yarmouth, Norfolk
(ADDED) Death found on FreeBMD:
CORKE Eleanor, age 81, Mar qtr 1931 Yarmouth vol 4b p14
The occupation of Ada in 1939 fits very nicely with the VAD laundress in Norwich Jan 1916. If this is her, there are three possibilities:
1) Ada SHEPHERD had an illegitimate child Raymond c1922
2) Ada (CORKE or unknown) married Mr SHEPHERD in or before Jan 1916
3) Ada (CORKE or unknown) was not married and in addition to Raymond born c1922 there must have been at least one other illegitimate child born in or before 1916 to explain the surname SHEPHERD. Did the VAD take on mothers of young children?