I’m the “victim” in this situation. My girlfriend hit me in the arm with a small hammer and I stupidly and drunkenly charged her. I immediately regret it. But it’s too late because the police came and charged my girlfriend with assault with a weapon. I don’t want to proceed with those charges. How do I drop the charges?

You may have to appear in court if your girlfriend was already charged and then the judge will decide if they want to proceed with a conviction for assault with a weapon or simply withdraw, drop or dismiss the charges.  Since your girlfriend was fingerprinted for this assault offence, she will need a file destruction to remove her fingerprints once you settle it in court.