Whats her problem??

i am 16 and in grade 10 this year and my best frind has just started hight school and she is in grade 9 this year, and she has made my grade 10 year horalbe bc no matter what i do she has to b so negative about what ever i do or what i were andif my clothes dont match and she has been such a snob and i have not been talking to her bc of the ways that she has been treating me and and she is getting mad at me even more i just dont wanna say anything ill regertt and now she is asking my friend rachel why i am being mean and not talking to her and all she told her was bc of what you have been treatting her and i dont know if its bc we like the same guy or what o dont realy care about the guy i care about her and i dont think she cares about me as much i care about her and i wanna say some thing to her but i just dont kow what to say any more so all i do is avoide her plzz some one help me :(