forgiveness

I'm having trouble forgiving someone who wronged me because the situation was completley their fault and their not sorry. last year i had a class with this girl laura, and there was a leadership position me and laura both wanted. i came to class everyday and prepared for it; she was absent all the time and did work in the class and wasnt even interested. she was so irresponsible that the teacher even said she would never give laura the position. when it came time for elections, laura's best friend stacy who currently held the position gave it to laura, and the teacher and laura's best friends approved because they said she was more "qualified" even though she didn't come to class. i've already graduated, but for my own sake, i can't forgive laura, the teacher, and her friends for doing something i think is totally unfair. a couple of students in the class even came up to me afterwards and told me they think i should have gotten it. i really just want to punch these people in the face. how can i get over this nonsense?