Okay, so just to try and organise what has been found so far:
The Adoptive Family:
1891 Census:William John Bryans (b.1866/7- Ireland) - Occupation, farmer
Eveline Annie (b.1866/7 - England)
1901 CensusWilliam John, Eveline & 3 Kids,
Stanley,
Rita &
Fanny1911 CensusWilliam John, Eveline, Stanley, Rita, Fanny,
Harold and
Maggie (b.1890, Origin- Scotch)
So, finally in 1911 we have Margaret/Maggie living with the Bryans, as their adopted daughter.
What do we know now about
Margaret.
On her marriage Cert, in 1915, she was listed as aged 24, making her birth year 1891
Her father was listed as W J Bryans, mother, E A Bryans So far everything fits

We have a photo naming
Christina Vickers as her mother, who died in 1900, when Margaret was 9 years old.
Ooh Polar Bear, your post has just come through, and you are way ahead of me!