Is this girl pretending to be my friend?

Most of the time we talk before school and also we talk in cles we have together and walking to cles and sometimes we talk at lunch and sometimes we sat together at lunch. But when we go outside not for recess after lunch she runs away from me to this other girl and when i try to go near her she runs away from me and in cl when we can work with a partner she never works with she works with this other girl and she leaves me by myself