well I think seeing a therapist would be a good idea so that this doesn't get out of control. you still have an awareness of what is going on and that your bpd is kicking in and you want to get a handle on it before it fully takes over.

I can see that it would be part bpd and part group dynamics. it is natural in groups that when new members come in that old members feels pushed aside. its the same reason three people have a hard time playing together. but you don't have to feel pushed out if you don't want to. call your friends and ask for that one on one time. it is not like they can read your mind and know that you are missing it. it is not like they know you need to talk. you are feeling left out and so allowing yourself to withdraw. don't. put yourself out there and let your friends know you still need them.