I cannot help you with a death/burial for Barbara Dewar, however there
is a record held by the New Zealand Society of Genealogists (St Johns
branch),
DEWAR, Barabara
Year: 1893
Event: Legal (other)
Source: Electoral Roll
Place: New Plymouth
Ref: Womens Suffrage
According to the reference there is a 'no charge' for the full record
if requested by email and you can email them at:
orders@sag.org.auAs the electoral roll shows her at New Plymouth and assuming this
is the same Barbara then perhaps New Plymouth may narrow your
search.
Good luck.
Mike.