Gazzy, I feel that you are truly obsessing about this at this point. It seems like your mind is wandering at 100 miles a minute trying to find some kind of answer, why she left, what you did, how you can fix it... please get yourself out of that space. It will do you no good.
I meant it when I said that she was only a part of your life, not your whole life. What did you do before she came along? Any sports? Hobbies? Dating?
I understand that seeing her around school is difficult, and by the way, her best mate ignoring you is more than likely a loyalty issue. Her friend most likely bares no ill will against you, but feels she needs to stick by her friend regardless... don't give that one much thought. Geoff is right, don't put a time limit on when you think you will get past this, there is no real gauge, but, it will take longer if you don't get busy with other things.
A lot of times what gets us down the most about a break up is that pebble in our shoe that is constantly nudging us, "what is wrong with me? why doesn't she want me?". It's not until we can come to terms that everyone is different and everyone needs and wants different things, and different is not bad. If my favorite ice cream is pistachio and yours is chocolate chip, it doesn't make me bad or wrong for wanting something else. When a new someone comes into your life, and she will, she may have some of the qualities of your ex-girlfriend, but she won't be identical, should your ex feel rejected at that point? Of course not.
Gazzy, besides going to school, we don't know much about you, what are your interests, your goals, your likes and dislikes? I ask because I, like others here, like to have a better picture of who it is we're speaking to... if you don't mind.