I want to know how to apply sociology or psychology to my situation?

Grow up, let it go. I don't know how old you are, but it's time to learn that life isn't fair and people aren't always nice, and there is nothing you can do about that. Playing childish games with this girl is not going to do anything for you. If your friends stop being your friends, then they never were. This isn't a matter of psychology or sociology, it's a matter of acting like an adult or being an immature child. Be an adult.