Ancestry.com. Scotland, Select Births and Baptisms, 1564-1950 [database on-line]. Provo, UT, USA: Ancestry.com Operations, Inc., 2014.
From Scotlands People (free registration)
Dennistoun is a district of Glasgow and the age fits perfectly. Unfortunately ScotlandsPeople will charge you £1.50 to see the full record.
Because it's Scotland, she was also registered under her birth name:
Name: MCLAUCHLAN, Forename: ISABELLA, Age at death: 89, Mother's Maiden Name: - , Year: 1956, Ref: 644/3 1019, RD Name: Dennistoun