The first thing that came to my mind when I read this is "These don't sound like friends." I know that maybe hard to hear, but I doubt you would treat people you liked this way- I know I would not. I think it I were in your shoes I would just say 'screw them'. I just wouldn't talk to them anymore, because that is not way to treat someone. If you don't want to be that drastic yet, then you could talk to them. If you think one of them is kind of the leader talk to her and ask her why they are doing this. I just wouldn't put up with kind of treatment for much longer. Good luck!
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I don’t want no part of your tight-ass country-club, you freak bitch!
That is exactly like all my girlfriends are from HS. I may talk to them online, saying how they miss me and blah blah blah. Then we all come home for ex: winter break and suddenly they are all busy or like one of my friends yeah i will call you tomorrow and we will hang out, never calls me, but then she goes out with my other friends. It is just annoying, i understand completely. Then when we all get back to school they say the same thing, i haven't seen you in forever and all that BS. I don't consider them friends anymore. If i were you i would distance yourself and make better friends.
Also though it makes you feel bad when they don't invite you places, that is how i orginally felt, like they don't like me for some reason. But then i took a step back and realize, do i really like them? Are they ever there for me? I mean it is nice to have people to go out with but it really isn't worth it when they are two faced.