My girlfriend gets blackout drunk from 2 shots spaced out over a few hours (potential reasons inside)

Okay so I should preface with saying my girlfriend has diagnosed OCD. Real OCD is a severe disease that absolutely destroys a person. I love her very much but worry the hell out of her health.

She has contimanation OCD. Without getting into details, she drinks ONE glass of fluids a day and has one meal (it depends, she was up to two a day but went back down).

She is also 5′ 1″.

Anyways, she very, very rarely drinks but the few times she does, she gets absolutely ANNIHILATED. One drink (she buys those cheap ass one ounce bottles at the gas station and just chugs them no chaser lol). After one drink she is like me 6 drinks in (I personally don’t drink alcohol, just not my thing, but if I did drink).

If she has 2 drinks I start to get legitimately worried about her well being as she will pass out and be very hard to wake. She’s also on no prescription medications.

We kinda agreed last time no more alcohol for her. But I’m not her father and with her enormous anxiety can’t blame her for wanting two every couple months. But damn….

What are your guy’s thoughts on this? The mix of empty stomach, small stature/weight and dehydration? Or something more? I mean I used to party pretty hard and she gets fucking wasteddddddddd. Like downing 5th of vodka. Crazy lol