What is the interpretation of seeing three dreams after performing Istikhara for a person who proposed to a girl, and then was informed that she would marry her cousin, and felt great distress?

The preponderant view after performing Istikhara is that the person should proceed with the matter, and not abandon it unless Allah diverts him from it. It is not necessary for him to feel a sense of relief in his heart or to see a dream. The fact that the engagement did not materialize is perhaps the good that Allah intended. Therefore, a Muslim should not preoccupy himself with dreams.