I do agree with what the above person said a lot of times it is that the ex boyfriend is back in the picture. You really do not know what the reason is though and it is hard to tell. Obviously she is not ready for a relationship.A lot of times guys just don't see no for an answer so maybe she is avoiding you for that reason? Just tell her that you are fine with being just friends and if she agrees with that... go out with other girls. Don't just waste your time waiting for her. And maybe when she is ready to date again she will let you know.