Did you just not turn up or did you say "Sorry but l've changed my mind and l don't feel like going"? lf it was the first, l can understand her being annoyed, though not to the barmy extent of ignoring you. lf it was the second, then she's got nothing to be annoyed about, it's just a disappointment. After all, parties are supposed to be fun, if you wouldn't enjoy it it would spoil it for her anyway. Either way, don't bother contacting her, just wait till she speaks to you.