Bad friend situation?

i hang around in a group of 8 friends and last year we were really close but now we've drifted apart . I'm still really close with one of them (shannon) but not the others. It's got to the point where they all go out with eachother all the time and never invite me or shannon. and also they can confide in these 2 new girls that they've known for a couple of months with secrets yet i've known them for six years and i'm the last to find out and i only find out months down the line. also they're really bitchy behind eachothers back. one time the 'leader' of the group (hannah) said to me and shannon not that i'm saying you are or using an example but it's like you and shannon going off together if you get me. (this was about these other girls because they were talking about how these girls weren't friends anymore). me and shannon can't just go and make new friends we've been in highshool for 4 years it doesn't work like that. but what should we do because i genuinely don't like some of them anymore.