someone help me stop my gf from drinking so much

So I’ve been dating this girl for around a month. We’re both sixteen, and we were having conversations like usual when alcohol got brought up. I started asking her this and that about how much she drinks and how often, and she told me she drinks 3–4 times a week, mostly vodka, which is fucking crazy to me.

When I drank a lot during the week, I just felt stupider. I’ve never really done alcohol like that, so I haven’t researched it much, but I do know it’s one of the harder drugs, and that doesn’t seem to get through to her. I’ve also noticed she has bad memory problems. She’ll ask me something on the phone, and sometimes it cuts out. Then, when she says I ignored her and I ask what she said again, she never seems to remember what she originally said.

Can someone please explain the effects that this amount of drinking at such a young age can have on someone, so she can get her head out of her fucking ass?