You have three basic options.  The first is to simply have your parents talk to her parents.  Many of these disputes can be resolved by people just talking.  Feelings tend to get even more difficult to resolve when someone calls the police.  However, if that doesn't work, you may want to file basic theft charges.  Your local law enforcement agency may or may not accept the case since you gave the items to your girlfriend.  However, it's still worth a shot-- and it doesn't cost you anything.  Your third option is to file a civil suit in small claims for the return of the items.  Usually before you file a suit, you will want to send a demand letter for the return of the items.  You may even want to consider hiring an attorney for the limited purpose of sending the demand letter.  People tend to take these letters a little more seriously.  Just know that once you hit the second or third option, that the chances of the parents ever approving will be slim.  So you really need to evaluate what is more important when you are deciding which option to use.