I don't like it when my girlfriend gets drunk
Why do you want to spoil the night for your girlfriend?
I want to avoid drunk people who are hard to control
It is good to be concerned for your girlfriend.   You should talk to them beforehand and have a conversation in private to avoid embarrassing them or creating further drama.
I'll see if that works.
Try not to sound too pretentious. You want to make sure she understands that you are on her side.