Is Cassandra a fortune teller, or is she just very smart?

Cassandra was very talented in being able to predict what is going to happen. Though she knew what she could do, nobody else did and never listened to her. An example of that when she told the person she was working for that his wife was having an affair and was going to kill him, he decided not to listen to her and brushed her off. Little did he know that what she said was true and he would soon die. Being ignored was normal for her though, because she had one hundred siblings! I know I wouldn't like having as little attention as she did. What kind of feeling do you think you would have to get these powers?