If she is self-centered tell her she is a flake and deep freeze her. Self-centered chicks if you ignore her will not care about what you think or care if you not part of her life anymore. So I agree with the others including lockdown and batman which is to throw a huge NEG out there and let it go.
If she cares about you as in you and her built chemistry and her friends like you and u k-close plus f-close her and then she suddenly becomes miss flakey. You let her know that she is flaking, you make sure its a cliff hanger NEG. One of those NEGs you know she is going to ask her friends about and they will spend days trying to figure you out.