relinquishment deed

Such cancellation is not possible unless it could proved that relinquishment was not voluntary but because of undue influence, misrepresentation etc.

I agree with expert Mr. P Venu, relinquishment deed is irrevocable and cannot be cancelled unilaterally.

When did she execute the relinquishment deed and why does she intend to backout, which smells / exhibits your greed for the property?

Using smell word without knowing facts not expected from seniors like u 

You can explore for filing declaration suit taking grounds of fraud, misrepresentation, undue influence etc., Contact a local advocate to explore such grounds that are legitimate