Excuses for not going to a party?

ok there is this girl who used to be my best friend but then she turned really nasty. Anyway basicly now she acts like i am not there but she has invited me to her party (probably because her mum made her) and last party was terrible, i had no one to speak to and everyone just blanked me so i really don't want to go. I can't just say i am not comming so can you think of any good excuses.