Her birth index:

Surname   First name(s)   Mother   District   Vol  Page
Births Dec 1924   (>99%)
Hearle Audrey    Martin Richmond S. 2a 757
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The only possible death on record is:

First name(s) AUDREY
Last name SINCLAIR
Gender Female
Birth day 14
Birth month 7
Birth year 1924
Age -
Death quarter 3
Death year 1977
District HYNDBURN & ROSSENDALE
County Lancashire
Volume 40
Page 1357
Country England
Record set England & Wales deaths 1837-2007

But the location is not near where her birth and marriage were.  So she may have been alive at least until 2006 when the online death register records stop.
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However from the will indices for 2006 onwards there are these deaths:

Surname First name Date of probate Probate number  Date of death  Document type  Registry

SINCLAIR AUDREY 16 October 2009 3135515 07 January 2009  Grant and will Ipswich
SINCLAIR AUDREY 09 October 2009 3124171 23 May 2009  Grant only  Newcastle Upon Tyne

Perhaps one of these will could be bought, but unless a son is an executor, it will not provide a clear identification as will indices do not include ages.
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Their marriage index:

Surname   First name(s)   Spouse   District   Vol  Page
Marriages Dec 1955   (>99%)
HEARLE Audrey SINCLAIR Wood Green 5f 1103
SINCLAIR John M H HEARLE Wood Green 5f 1103
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