Can a wife claim share in mother in laws property

My wife is seeking will challenge and permanent stay in property which is in the name of my mother. My mother had got inherited this property through an unregistered will signed my father(before father's death) and such property was purchased by dealer. After fathers death, i and my sister surrender our share by giving affidavit and mutation was passed in favour of my mother. Property tax assessment, elec. bill and intakaal in patwari record is in my mothers name. Now my wife is seeking will challenge by saying that i surrender my share so that she cannot take share from the such property. Moreover she is threatening also to register FIR U/s420. Pl advice, is she liable to challenge as she is not class 1 legal heir. Mutation of such property was never executed in my name. Can she take any stay or challenge it in any court or not?