The Church of England has published a special prayer on the death of HRH The Duchess of Kent. You can also read this statement from the Archbishop of York.
Almighty and eternal God,
Lord of life and conqueror of death,
receive, we pray, your servant Katharine,
whom you have called from this life.Grant her a share in the inheritance
of the Saints in light,
and comfort us who mourn her passing,
that, strengthened by your grace,
we may trust in your Son,
who is the resurrection and the life;
through the same Jesus Christ our Lord.
Amen