My friend is trying to friend me on facebook but i dont want to be her friend anymore?

ok so i just finished 6th grade but i only had two friends!!!!! one had been my friend since the 3rd grade but the other one was mean and crude. i tried to get rid of her the whole year but i was her only friend! i just want to start fresh i am going into middle school so i am hoping i don't get in any classes with cristina (the mean girl). just tell me if i should friend her tell her i don't want to be her friend then un friend her or just ignore her completly. PLEASE HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!…