Most individual records of deportation from Canada don't survive, unfortunately. There is a book called "Whence they came: deportation from Canada, 1900-1935" available on Google Books which shows a nice table of deportation cases and their causes:
1910: medical 212, public charge 348, criminality, 130, other civil causes, 44
1911: medical 222, public charge 289, criminality, 179, other, 83, accompanying (canadian born children of those deported) 18.
If her husband had died or abandoned the family, she could have been deported under the "public charge" heading. I see she was heading to Toronto with a son Peter and a daughter Jeannie - son Peter appears possibly to be in some sort of children's home in Toronto in 1911.