if your friend started being mean would you still be their friend ?

Hey, listen. A real friend is someone who never turns their back, who is there for you always, no matter what. If you always had doubts about them, they probably aren't a real friend. I'm really sorry. If they've always been like this, do you really want to stay with them?
However, everyone has bad days, and friends do stay together through thick and thin, and that includes fights. So if he/she is just going through a phase, stick with them. It might turn out all right.
'Those who mind don't matter, and those who matter don't mind.'