My friend had a sweet 16 yesterday and she didn't invite me. I have been friends with her for a long time, last year we used to eat lunch together everyday at school and I don't understand why she didn't invite me. I didn't do anything to her. Does she hate me? Why wouldn't she incite me?

The only person who knows the answer to that is her. She is the one you need to ask.

Perhaps it was her mom or someone else who did the invitation. And what types of friends are you NOW, not last year ? If their family is from a rich family? What is yours, I know when my mom had parties for me, often people from the "wrong side of the tracks" were not allowed since she was paying for the party.