If you are sure she is buried I would first suggest you contact Torfaen Borough Council in Pontypool as they control the largest Panteg Cemetery in New Inn, Pontypool which is likely for a 1972 death, Panteg Cemetery is now closed to new entrants, you can only be buried now in an existing plot.
Do you know where she died and area she was living as it would give a possible clue to a burial place if not at Panteg.
Gwent Records Office now in Ebbw Vale has newspaper archives and you may find an obituary for her with further clues.
Also Gwent Crematorium was operational in 1972 and I believe their records are now online at
www.gwentcrematorium.org.uk go to book of rememberance then search, enter name etc
I can only find a Mary Louisa Lane born 1923 and died 1984