My sister is schizophrenic. For several years, my parents believed in fortune-telling bodhisattvas and paid people to come home to tell their fortune. Can they trust fortune tellers?

Have faith, but have no faith. Generally, people who can decide their fate are people whose fate has not changed much, but there are two kinds of people who are not. One is a person who does evil, and the other is a person who does good and accumulates virtue. Look at the Four Disciplines of Fanfan and you will know how fate has changed. If you have tried psychological intervention and other treatments for your sister's problems, it is still not good. I suggest that you can ask monks, especially eminent monks and great virtues, to help you and bless you!