Before the Whitebeard War, Shyarly predicted Whitebeard’s death and he indeed met his end.
She recently made a prediction that a man in a straw hat, who she presumes to be Luffy, will destroy Fishman Island.
However, Luffy left Fishman Island without destroying it so that prediction has not come to pass. But since events that Shyarly foresaw can happen anytime from a day to a year later, there is still a possibility that Shyarly’s prediction is not wrong yet.