This certainly works better according to the Maharsha who says that the Chasid saw all of this in a dream. Since we know that "Ain Chalom Bli Devarim Bitailim" loosely translated as "There is no dream that does not include some incorrect details," it would appear that it is permitted to say over a dream even if the dream indicates that a different person had something bad happen to him in the past. Indeed, most people who would hear such a thing would say, "it was just a dream." Only after the dreams came true did the wife of the Chasid relate this information to the mother of the girl with whom she was fighting.

Alternatively, it could be that it would be permitted to say this if the woman was told that her daughter received a better burial. If she paid money for this burial, she indeed is able to have a legal claim on the Chevra Kadisha or whoever buried her for not giving her a better burial. Accordingly, it would be permitted for the chasid to tell his wife in order for her to tell the woman that her daughter did not receive a proper burial, so that she could claim a better burial from the Chevra Kadisha or whoever buried her. Even if they would not open the grave and take away the Machatzeles, they would very possibly owe her money.

All the best,

Yaakov Montrose