Question remains: where did her husband Alfred Edward Giles go? I've accumulated a number of bigamous relationships along the way and it isn't always as simple as it seems. Divorce was very expensive and very difficult to obtain. It also seems that if the couple had been split for ten years - and they could claim that they had no idea where their ex-partner was or even still alive, then the subsequent marriage could well be considered not bigamous. The ten year gap between the 1901 census and the 1912 marriage could well justify that.
Have you ruled out the man in this couple? They appear in a number of trees on Anc.
Alfred Edward Giles and Zillah Jane Hoare. There's no apparent marriage for the couple but they appear to have had 7 children between 1905 and 1919.
1949 Q4 Death - Alfred Edward Giles; age 83 (born c1866); Battersea; 05C; 83
1953 Q3 Death - Zillah Jane Giles; age 77 (born c1876); Wandsworth; 05D; 530
1905 Q4 Birth - Ethel Zillah Giles (mmn: Hoare); Lambeth; 01D; 419
1908 Q1 Birth - Mabel Doris Giles (mmn: Hoare); Lambeth; 01D; 371
1910 Q2 Birth - Dorothy Winifred Giles (mmn: Hoare); Lambeth; 01D; 392
1912 Q3 Birth - Margaret Emily Giles (mmn: Hoare); Lambeth; 01D; 725
1914 Q4 Birth - Zillah Edith Giles (mmn: Hoare); Wandsworth; 01D; 1189
1916 Q1 Birth - Sydney Lawrence Giles (mmn: Hoare); Wandsworth; 01D; 1179
1919 Q2 Birth - Phyllis Alice Giles (mmn: Hoare); Wandsworth; 01D; 812
1911 Lambeth
Alfred & Zillah
+3 children
https://www.familysearch.org/ark:/61903/1:1:XW5S-LF4Zillah and family in earlier years:
1861 Q3 Birth - Francis Lewis Hoare (mmn: Waring); Woodstock; 03A; 556
1863 Q2 Birth - Agnes Eliza Ann Hoare (mmn: Waring); Woodstock; 03A; 585
1867 Q4 Birth - Elizabeth Mary Hoare (mmn: Waring); Woodstock; 03A; 608
1869 Q1 Birth - Albert Job Hoare (mmn: Waring); Chipping Norton; 03A; 735
1870 Q3 Birth - George Hoare (mmn: Waring); Chipping Norton; 03A; 679
1874 Q2 Birth - Ralph Eric Hoare (mmn: Waring); Chipping Norton; 03A; 722
1875 Q4 Birth - Zillah Jane Hoare (mmn: Waring); Chipping Norton; 03A; 711
1879 Q3 Birth - Mabel Edith Hoare (mmn: Waring); Chipping Norton; 03A; 764
1880 Q4 Birth - Emily Miriam Hoare (mmn: Waring); Chipping Norton; 03A; 758
1883 Q3 Birth - Hubert Hoare (mmn: Waring); Chipping Norton; 03A; 808
1883 Q3 Birth - Rose Hoare (mmn: Waring); Chipping Norton; 03A; 808
1898 Q1 Birth - Evelyn Mabel Shaper (mmn: Hoare); Pancras; 01B; 149
1900 Q2 Birth - Frederick Shaper (mmn: Hoare); Lambeth; 01D; 462
1881 Chipping Norton
Zillah
with parents Lewis and Mary
+siblings
Ref RG11; Piece 1520; Folio 48; Page 23; Schedule 666
https://www.familysearch.org/ark:/61903/1:1:Q27H-145J1891 Clerkenwell, Holborn
Possibly Zillah (birth place differs)
Servant in Whitehill household
Ref RG12; Piece 229; Folio 50; Page 48; Schedule 351
https://www.familysearch.org/ark:/61903/1:1:3RB1-43Z1901 Clapham, Wandsworth
Zillah
with married sister Bessie (Elizabeth Mary?) and her husband Frederick Shaper
Ref RG13; Piece 464; Folio 140; Page 25; Schedule 154
https://www.familysearch.org/ark:/61903/1:1:X9CC-387EDIT: Corrected number of children (6 => 7) for Alfred and Zilliah