Girlfriend (22f) won't let me (24m) drink on Halloween weekend

Hey guys as the title says my family is having a Halloween party at the end of October. Typically my family enjoys drinking, as do I. My girlfriend of, 7 months plus situationship of 4 months, does too, so there is where the problem comes in. We like to be safe and usually take turns drinking.

My town festival was 3 weeks ago, and she lives close enough that we could walk. We walked with the intention of drinking a bit more than we usually do. My girlfriend however is on the shorter side, so if she drinks as much as I do she usually feels it a bit more. This in turn causes me to limit how much I drink, so I can look after her if need be. So I ended up having to pretty much hold her up when we went back to her house at the end of the festival.

This past weekend it was also one of her friend's birthday. We both went and before hand agreed we'd stay for a couple hours. Well when I was off playing Fuze ball with mutual friends I came back to find her really tipsy playing drinking games with the birthday girl and her other friends. Basically she got peer pressured into it. Honestly I kinda knew it would happen so it wasn't that big of a surprise. Especially since it'd been awhile since she's seen her friends. Well at the end of the night, more than a couple of hours later btw, a mutual friend, more mine than hers, invited us to his Halloween party.

Now we're discussing how we're going to work out who gets to drink at my family's Halloween party and my friends Halloween party. I'm saying that they're both my turn to drink seeing as she drank more at the festival, and was the only one who got to drink at her friends. She's wants to drink at one of the functions which I'm not opposed to, but then she'll have 3 more times on me.

Do you guys think I should just give in or tell her that it's my turn to drink at both functions?

TLDR girlfriend would like to drink at one of the halloween functions, but I would like to drink at both for it to be fair.