Biff's second wish was granted to the person closest to him, which was Melissa.
She looked wide-eyed at her two friends (Amber and Jessica) and then at all the other girls who looked just like them. All of a sudden she knew why they all looked the same. She never really even thought about it before. She just took it for granted. But now she knew the truth.
It was all because of a wish. She knew that sounded insane, but she knew that that's what it was. A wish. Someone wished that all these girls including herself would look like Sarah McMillan. And it came true.
Suddenly, Melissa started to question everything that she thought was real. It was like her entire life was a lie. She started to feel like she didn't want this knowledge of the truth. If only she could forget ...
Then, without really thinking, Melissa said "I wish ..."