Pulling someone's hair is a crime; pulling your girlfriend's hair is domestic violence! And making that kind of statement can get you jail!
You should hire an experienced criminal defense attorney in any case to help you avoid a conviction and the 3 years probation and 1 year of DV classes that are mandatory!
Pulling your girlfriend's hair would generally be considered domestic violence assault. You are strongly encouraged to speak with a lawyer to advise you of your constitutional rights regarding your charges in LA County. Hopefully, you did not incriminate yourself to law enforcement.