Her grave should be in Ireland.
According to publications in press she died on 14th October 1996. Funerals took place on October, 22 to Tunbridge Wells Crematorium, England. But Crematorium says that shortly after the service her remains were removed. They don't have records by whom and where.
I suppose that her remains were sent to Ireland in Glenkeen graveyard, but she is not mentioned in Records from Glenkeen
http://tipperarystudies.ie/wp-content/uploads/2016/12/Glenkeen%20Gravestone%20Inscriptions%20reduced.pdf May be they are not full, they are made in 2004.
Her husband Seamus Burke (Tipperary TD, 1918 – 1938) is buried in Glenkeen:
James A. Burke B.L., Rockforest, Roscrea died 10th June 1967 aged 74 years
Her daughter is in Glenkeen as well:
Natalie Isabella Burke
born 17th January 1930
only child of
James and Zinaide Burke
died 12th December 2012
I found an old topic about the genealogy of the Sumarakov-Elston genealogy (Zenaide is from this great family):
http://forum.alexanderpalace.org/index.php?topic=3004.0 Her grave is mentioned there, but no location.
Where can it be?