My best friend is angry at me...?

If she is not returning any of your calls/any methods of contact give her a few days to calm down. Then approach her face to face and let her know that this situation needs to be taken care of. Whether it be talking w/ each other in a quiet area or over the phone, communication is key. If she refuses to try and work out the situation w/u then she may not be as close of a friend as you thought. If that happens to be the case I'm sorry, but remember that in your life you will only have 3 true friends that would give anything for you. You are still young and may not have found all of them yet. Good luck.