Why should we even know each other from the start? (EXO Chen fanfic)

Why should we even know each other from the start? Jocelyn and Chen were friends since they're young. Chen was known as the troll, always messes up with the other people. He enjoys teasing Jocelyn, and playing prank on her. Jocelyn was thinking about, why would they even know each other from the start. She started to think that she shouldn't become friends with him. But when one day Chen confess to her, she don't know what should she do.