I am the granddaughter of Elizabeth Ann McCarl (nee Turner) born 1905 in Scotland. My grandmother was the youngest daughter of John and and Isabella Turner and younger sister (by two years) to Mary Atkinson Turner. A few times in my life, I heard my grandmother speak of her sister who mysteriously disappeared from her bedroom one night. It was a very upsetting time for the family, as Mae (so she was called) had young children at the time and there appeared to be no reason for her disappearance. My grandmother was especially affected because she and Mae were very close, if Mae had planned to disappear she would have confided in her younger sister. This haunted my grandmother all the rest of her life and remained a mystery to her until her death. If you find out anything at all, I too would be interested to hear.
I believe that your grandmother Mary was called Mae by her family, at least by her younger sister Elizabeth. I have an old photo which was left to me in my grandmothers belongings when she passed away in Guelph Ontario in 1987. The photo has written on the back: John and Isabella Turner, Mae and Elizabeth, who would be their youngest children. The writing was put there by my own Mother Jean Ann Close (nee McCarl), third oldest child of Elizabeth McCarl (nee Turner). There is no date on the photo but I know that Elizabeth and Mae look to be pre-teen in age. Not sure if the photo would copy well since it is so old.
Just though you might be interested to know that Mary's disappearance remained a mystery to her closest sister.