Thank you all for your help.
The marriage which Haydon found in Pontypridd is correct.
Finding her place and date of birth is proving to be illusive. I have searched the 1911 census and there is a Nellie Scanlon as a lodger living with a Ann Harrington in Pontypridd. She is stated as being a visitor from Kerry Ireland. She is the right age of 13.Maybe she was in service to Mrs Harrington who is stated as being a widow So I think the Nellie Scanlons from Newcastle are unlikely to be my gran. I have found a number of Nellies in the Irish censuses and baptism records. However,without a date of birth, I can't go any further. That is why I am pinning my hopes of a date of birth on her grave stone.
Can any one suggest any other records I can access where I can find her birth date and place of birth.
Thank you for giving a reference for my grand mothers burial plot. From this, I have been given a contact who can find out if there is a grave stone with the dates I need to continue my search.