I think if she missed her opportunity to get cops involved. If she were going to do that, it seems like she would have done that when her emotions were higher. After, I think after this long together, this will not be the way she thinks of you after the dust settles. There is too much good history for that.
Have you SEEN her since the incident? A fat lip usually heals pretty quickly. I would wait to cut contact formally until there are no physical signs of your altercation, just in case she becomes vindictive.