She is 89. Dada and her were married for 69 years and after his passing has started talking about being ready to die. So telling her at this time seems cruel.
But telling her and giving her time to resolve this Karm ( if it was created at all ) is that way to go or letting it go and working on my own feelings is the right way to go? Will giving her chance to resolve this Karm help in her evolution. Or this was not Karm at all and will dissolve as minor matter?
She has created karma by attachment and its inevitable result is suffering regardless of the nature of attachment.
It is not good to judge people and give our views until they ask. You can tell her you have been hurt to clear your grudge but it will create pain and guilt in a lady who is growing old..
Best is to offer it all to the Divine Grace and leave her, yourself and others to go through the lessons of Fate..
Affectionately,
Alok Da