What census in what country are you speaking of? Would it be England or North America? Do you have a county as a reference point as to where the census was taken?
There is a possibility she may have died before 1880. Do the church records have any reference to a cemetary close by? If you are close to that location, check on the cemetary records by contacting a trustee. There may also be a possibility they were divorced. Does it show that James Ridley had another wife after 1880?
These are some sources you could check out. Good Luck!