Actually, you can't drop the charges, only the prosecutor can do that. You can tell the prosecutor that you don't want your girlfriend charged, but they frequently ignore the victims when they say this. Politics are involved and the prosecutors do not want to appear to be soft on domestic violence. Assuming your girlfriend did not cause serious injury and did not use a deadly weapon, she should be charged with simple assault, which is a misdemeanor, usually punishable up to 1 year in jail and a $5,000 fine. First time offenders are more likely to have their jail sentences and fines suspended and be placed on probation for a certain number of years. She may be required to take anger management and/or domestic violence classes as well.