Umm excluding the person that is your mate from a closed friendship ring is questionable at best. You keep taking this on as if these are "just" your feelings as if they don't count, as if how this is affecting you is a non issue or something and that's pure bs. If you are a couple the fact is YOUR MATE should be your #1. New Years is a big deal and I'm sorry just as the others have said this is friggin weird azz behavior.

Everything you feel about this, excluded, as if her clique is too good for her to include you in, as if something else is going on, IMO are perfectly natural and on top of that JUSTIFIED feelings and need to be addressed. If anything You needn't be questioning your behavior or feelings in this but hers. What is it that she is doing with these friends that you wouldn't approve of or that she's hiding. I'm sorry to be blunt but really that's what seems to come to mind for me.