I'm going to ask my girlfriend to not drink alcohol at all at a new years party I can't attend myself
Why would you ask this of your girlfriend?
I plan to have people spy on her and report back to me.
Your girlfriend is her own independent person and it's not right for you to demand she behave in a certain way. Having people spy on her alarms me and I think you should take a step back and recognize that your actions are controlling in a way that isn't healthy.
Fucking hell, who are you to tell me what to do.
I'm not telling you what to do, I'm informing you that she is an adult and drinking alcohol is her choice, not yours.