Hi Steve,
Robert Telfer and his family, including grandchildren, are still in Harraton on the 1891 census. An Isabella Telfer, age 33, is recorded as being his daughter.
By 1901 The family are in Chester le Street. Presumably Robert has died. Isabella is head of the family, Roberts grandchildren,Robert age 23, John, Walter, Jane Ann and Thomas, age 6, are recorded as Isabella's children.
Her status is "widow".
I'll do a bit more digging to see if I can find anything else. Apologies if you already have this info.
Kathleen