Jessica
1) Remind her she was Mike's second choice.
2) Remind her about that day after the movie where Bella could have gotten both of them killed by talking to the strange men.
3) Remind her that the "new girl" got gorgeous Edward Cullen and he didn't show any interest in her.
4) Tell her that Bella was more special since she threw an awesome graduation party.
5) Remind her Bella is better than her by making it into Dartmouth.
6) Remind her that Mike, Eric, Tyler, Edward, and Jacob all would rather have Bella than her.
7) Tell her that if Bella hadn't told Mike to ask Jessica out, he never would have.
8) Call her boring.
9) Tell her that Bella is friends with the most beautiful people (coughvampirescough) in school.
10) Just flat-out tell her that you like Bella better.