Have added some data on her profile, the problem is mainly that births for the period are not yet indexed. So without more info on location and the province, no way to tell more. I did find record of her death which gave a specific birth date, although that has to be taken with a grain of salt, funeral records don't always get it right.
You already have the sister Ida Maud, who married in Montréal the same day as Mary Ann. There is also a brother who marries in 1912, Allen Cornelius Butler, of age, married Myrtle Evelyn Thornley 13 April 1912 in St-Gabriel church of Montréal. (Drouin collection)
I think you are going to have to search census records for the family before these marriages, 1901 census is available online from Library and Archives Canada, that may tell you origin of parents.