Hi
To try and narrow things down have found this info-
Burial Glyntaff Pontypridd Elizabeth Lewis year 1928 plot no.N.0147 burial ref 20191
In the same grave buried Robert Lewis year 1924.
Looked up BMD there are two Robert lewis's
Robert Lewis aged 65 vol11a page 533
.. .. aged 71 vol 11a page 570 both pontypridd district
Do you have a connection to either of these Robert's and and the Elizabeth buried with him is your great grandmother?
Other suggestion have you checked your grandmothers ages in all the census's because ages can change from one census to the next.
I hope this is of some help
cheers cardiff
