No no no no no.... that first scene was imho a critical mistake. What it clearly established - to me at least - is that she was gorgeous and in the popular-girl-set at school. There was a mistake, but her reaction was to roar her head off laughing with her girl-friend - "as I've I'd call that loser GORGEOUS?!" If she'd really been sweet and altruistic, that reaction would have been awkward or embarrassed laughter, not laughing AT him. And that first impression is absolutely critical in a movie.
The other problem, as others have pointed out here, was the "gay" plot. That was really dumb. It puts her character in a bad light cos she looks so stupid. There was zero evidence that KA was gay, and yet she believes it just cos she was told. She didn't even attempt to eek out the truth for herself. At the very least, I'd want an acknowledgement that when she finRAB out the truth, she felt stupid.
All round, she was a very weak character. All she was really there for was to be gorgeous (which admittedly she was) so we're happy for KA when he gets her, and to motivate the later story point that he now cares for someone for the first time. She could - and should - have been so much more.