Hi
I think I have found the Walker family in the 1916 and 1921 Canadian censuses in Lethbridge, Alberta. Margaret is with her brothers Peter & Adam, and, in 1916, also in the household is their mother Catherine. Margaret is on the 1916 census as Maggie Walker age 30 and in the 1921 census as Margret Walker age 40. It would appear that Margaret did not marry until after 1921, someone more familiar with Alberta marriages may be able to advise where to look for a marriage, and what information would be on it.
I have found an obit for Peter Walker from the Lethbridge Herald 9th Nov 1953 which mentions his brother Adam and two sisters Mrs Tom Mccreath of Red Deer, and Mrs Mary McCormack in Glasgow Scotland. If you PM me your email address I will send a copy of the obit.
I think I have also found the Walkers in the 1881, 1891 and 1901 censuses in Perthshire, Scotland. The fathers name would appear to be James Walker. According to the 1891 and 1901 census Margaret was born in Dull, Perthshire. She is on the 1891 census as Maggie Walker age 5 and on the 1901 census as Maggie Walker age 15.
Andy