I have a problem with my best friend?

we are in different grades iam in 10 th shes a 9th grader and we hung out since the first day of school but now she dosent tal,k 2 me or even sit with me what should i do move on or should i just like do what she does i mean she hangs with a girl she claim she doesnt like .............................please help me i am pissed off 10 pts for tha best answer tahnkm u