Once I was at a family bar mitzvah and a cousin said that yesterday (which was Shabbos) she dreamed a figure of a woman came to her and said she was the Tzailimer Rebatzin and she was unhappy because since she had no children, no one came to her grave on her yurtzeit. Another cousin said that she also had a similar dream the day before. Someone checked the calender and it seems it was a few days before the yurtzeit. You can be assured that people made sure to always go to the kever on her yurtzeit since then.
I know other people who have had dream that were true.