OK, Mary Margaret O'Grady and William Topping DID have a daughter, also named Mary Margaret, as well as a son, William John

1913/C5831 Mary Margaret Topping - William - Mary Margaret O'Grady
1911/C1862 William John Topping - William - Mary O'Grady

Now up to sort out which one, mother, or daughter, might have been the one who married Melville Spence. :)
Gloria