Yes, yes, yes! Thank-you for the suggestion. A previous search I carried out in FindMyPast, based on name and age, did come up with a record in Bristol, which is not far from the home town of the subject (Chepstow), but I didn't follow it up at the time. I've just been on there again and used the advanced search facility and entered the address in Bristol, and sure enough, there she is, living with her daughter and son-in-law, thereby confirming I've got the right person. However, I'm perhaps still struggling with the death cert. I'd like the death cert. to possibly confirm that the subject lived to the grand old age of 96 - and that I've got the right person.
The person in question is Elizabeth Kennedy (nee Stephens), born 1862 in Chepstow, and the death record I'm wondering about is Elizabeth Kennedy, died 1958 in Cardiff.
Thanks again for the 1939 suggestion. I'll get that document at least.