it can be really hard to get over a person u truly liked...try to keep urself occupied with fun activities until time passes. try not to be friends with her if you guys are still nice to each other this will only bring on lonesome feelings and a want for a relationship again. if she hurt you once it will probably happen again. so, let the time pass and find a new person. trust it can get better then her.
Breakups are very hard to get over. Every person deals with emotions in various ways.
To keep your mind off from her it will be hard but you need to keep yourself active. Start hanging out with your friends a little more or find a rebound. If you find a rebound don't rush into things.
After caring for someone for a bit then losing it can be stressful. Life is full of ups and downs. This is just a down for you but as time comes you will find someone that is right for you and you'll be with them forever.
the same thing happened to me before. i went out with this guy for a long time and when we broke up it was very hard. at first we were still friends but it was very uncomfortable for me. The best thing you can do is take time apart from her. keep your self busy, you need time to heal and get over your relationship.