What to do with my Girlfriend? Who is wrong?

Ask her that if the role is reversed, how would she feel if you keep going to your ex girlfriend/best friend for advice and help instead of her. Tell her to think hard on that. And then consider your feelings whenever she feels like running to him instead of you. You are her boyfriend, not him. If she still clings on him whenever she needed someone, she is obviously not ready for someone new in her life. Tell her that you're not trying to force her into choosing between you and her ex, but she is close to stepping over the boundary here and you are hurting because of her actions.