Do i tell her that we need a break? Or should i start doing the same thing to her and see how she likes it?

So me and my friend have been like sisters for the longest time now, and we just recently this summer started hangingout with a few other girls and, my bestfriend has gotten so obsessed with being exactally like one of the newer girls. All she ever does is fallow the other girl around and always has to do what she does and says what she says all of the time. Im fine with them being close, im actually happy, But she has gotten to the point where she leaves me out all of the time, and she blows me off. I hate it, and she always such a ***** to me And i dont know wether i should do it back, or just tell her that we shouldnt hangout as much anymore. Or.. If i should not say anything and just stop hangingout with her.