TIME Magazine reports Rauch only recently learned of the decision — which effectively reinstates their marriage in the eyes of the Catholic Church.
She had charged that the annulment was dishonest and only given to Kennedy because of his family's influence.
The couple divorced in 1991, and Kennedy married his second wife in a civil ceremony in 1993.
But he had sought the annulment in order to be married by a priest and continue receiving church sacraments.
TIME reports that the controversy surrounding the annulment may have contributed to Kennedy's decision in 1998 not to seek reelection.