Best friend problem. How do I approach it?

If she is that quick to de-friend you then she is not your best friend nor a friend at all. That aside, if you want to forget about the bad event you should close out or not post on twitter, facebook or the like. These sites set you up due to their nature. Look forward to the new school year and try to do an after school activity or join a study group. Any group activity that is based on a positive goal will be much more beneficial to you than all the blog sites combined. Good Luck