For Grace Gertrude Secker, I think she married on the day of her arrival in Australia! From that newspaper notice we had on the other post, the marriage date was 27 June 1880. This looks a possible shipping entry for her arrival:
Miss Grace Secker, 24, arrival port showing as Adelaide, Melbourne and Sydney on 27 June 1880. Left from London on the Liguera.
No messing around on timings here, so has to be they romanced at home
From that marriage notice, both their parents, Charles Andrew and Samuel Hecker are already deceased, which fits with what we have for Mary Andrew in 1881.
Big Secker family in 1861 living in Wakefield, everyone showing as born in Wakefield apart from Samuel:
Samuel Secker 47, general practitioner b. Ryhill, Yorkshire
Elizabeth Walker Secker 41
Ada Emeline Secker 18
Maria Louisa Secker 17
Agnes Mirian Secker 15
George Herbert Secker 12
Walkr Vernon Secker 11
Samuel Wilfred Secker 9
Elizabeth Burrell Secker 7
Arthur Wellesley Secker 6
Grace Gertrude Secker 3Charles Ernest Secker 2
Alice Maude Secker 1
Ref: RG9, Piece 3425, Folio 57 Page 7By 1871, Grace shows as a pupil and living in Knaresborough.
Her father shows as widowed by 1871. The family mis-transcribed on the index I am looking at Jecker/Secker, and living in Wakefield:
Samer D Jecker 57, surgeon and general practioner b. Wraby Yorkshire
Arthur Wellesley Jecker 17
Elizabeth Burnell Jecker 18
Charles Ernest Jacker 12
Henry M Secker 10
Mary Ann Secker 58, sister b. b. Wraby Yorkshire
Arthur Billinson Secker 19, assistant
Mathree Ellen 25
Ref: RG10, Piece 4625, Folio 72, Page: 13