My girlfriend wants to get high..help?

My girlfriend wants to get high "Once" on weed just to know what it feels like. I keep trying to explain to her why she shouldn't and it's been hurting me knowing that she might.. I wouldn't be able to stand it if she got addicted to it.. I know some People that have done/do it and say the only addicting part is having fun with your friends.. What should I do..? Were both 16