Have you checked the 1939 register to see where she was living?
Grace Sarah Harrison
Address
1 The ParadeYear 1929/30
Constituency in full Parliamentary Borough of Hythe
Polling district or place Folkestone
Record set England & Wales, Electoral Registers 1910-1932There are other persons listed at this address so perhaps it’s a boarding/lodging house,
unfortunately the year only goes to 1932 so can’t check for an address for the year 1955

Edit to add
I've checked findagrave, billiongraves index and deceased online and can't find anything for Grace sorry

Could she have been buried with family members?
Do you know where her parents/siblings are buried?