Will they ever believe the truth>

When children grow up, they forget many things, either because their love for the person is blind or they honestly forget. A parent does not want to bad-mouth the other parent, and her children grow up with a different picture.  This happens many times. A woman is accused of being the bad one, lies are told.  children  grow up thinking it's their mother's fault, the  grandchildren are told the wrong story, what is a person to do?