I found this site and it gives the 1901 and 1911 census for 1911 Census Mullaghderg Mountain, Templecrone.
What is interesting is that Mary HArley is aged 51 when Daniel is aged 4. This I think would be improbable. However, Mary aged 24 seems to fit better. Maybe it is possible that she wasn't his sister, but rather his Mother. In which case, Mary Harley 24, may have been your grandmother.
Madge O'Donnell Head R.C. 92WidowerDonegal James Harley Son-in-law R.C. 60 Farmer MarriedDonegal Mary Harley Dau R.C. 51Married 32 9 9 Donegal Denis Harley Grandson R.C. 28 Farmer's Dau SingleDonegal Mary Harley Granddau R.C. 24 Farmer's Son SingleDonegal John Harley Grandson R.C. 19 Farmer's Son SingleDonegal Charles Harley Grandson R.C. 15 Scholar SingleDonegal Madge Harley Granddau R.C. 12 Scholar SingleDonegal Joseph Harley Grandson R.C. 9 Scholar SingleDonegal Daniel Harley Grandson R.C. 4 Scholar SingleDonegal