Make the first move. Regardless of who is in the wrong, taking the first step towards addressing the issue shows her you are anxious to resolve the conflict. If you believe you are the guilty one, then apologize sincerely for your actions. If you believe the blame lies with your girlfriend, do not offer an apology, but rather tell her you love her and want to work towards resolving the issue.
Listen to what she has to say. She may still feel angry and upset, but it is important you let her get all of her frustrations off her chest. Avoid trying to get your side of the story across; this is likely to reignite the argument, as well as give her the impression you are not interested in what she has to say.
Give your girlfriend some space if she needs it. If she is still angry about the fight, your only option is to give her time by herself to calm down. Trying to talk to her when she is angry means she is unlikely to listen to you or may say something she doesn’t really mean, leading to further conflict.
Walk away and leave the ball in her court, if she says she does not want to talk to you or does not accept your apology. Forcing her to have a conversation she is not ready for only serves to further isolate both of you. Instead, let her know you are willing to wait as long as it takes and tell her to get in touch with you when she is ready to talk. Once she has thought about things logically, she can approach you and you can both talk about your issues calmly and hopefully reach a resolution.