I need help with friend trouble?

Okay so this year I made a new friend (lets call her Sally). I really want us to be best friends but there is this other girl (Lets call her Sue) that Sally is always with. Sally won't answer my texts. Sue and Sally always talk about there fun sleepovers and stuff and its really heartbreaking. Sally still waits for me at my locker, talks with me in homeroom and stuff but I always see them off together. I want Sally with me and Sue gone. Can anyone help?