1. Your mother cannot cancel the gift deed now. ONce a gift deed is executed it results in an instantaneous transfer of title to the donee, and the donor thereafter ceases to have any right, title or interest in the property. So if she has to cancel the gift deed then she is required to file a suit for cancellation in the civil court, which you can contest fittingly.
2. Since your mother is refusing to execute the rectification deed you may file a suit for mandatory injunction against her.