This is a sad situation. The new wife has not placed any blame on the aunt that carried the "gossip". Was she at the wedding? Talk about trouble maker....... 
If this son decides to carry on this negative relationship due to his wife's feelings toward his mother the wife will someday feel the repercussion of this hate.  
What goes around, comes around!!! 
Mend fences, start anew. You can not forget but you can forgive, and that goes to all parties involved. 
Dr Phil is right, don't wait until someone dies to say I love you and yesterday is just that yesterday. 
Yesterday is gone, tomorrow is a mystery, today is the present. Accept the gift of today, treasure the love we are blessed with. Someday this young wife will learn that a mother (and or son) will not always like what each other does but they should always love the person, even if the do not like their actions. 
Theresa hopefully your future daughter and/or son-in laws will be more caring for you and forgiving than you are toward you husbands mother. Watch out for that aunt that thought she was doing you a favor.