she’d drunkenly hooked up with a man last night

We have only been dating for a few months. She’s an alcoholic

Ok, this is easy, obviously you break up since it's only been a couple months and she's also an alcoholic right?

I’m gonna guess this may be a result of her looming treatment and maybe some form of self sabotage.

So wait, you're making the excuses for her? Even if that's true why would you stay with someone that is sabotaging your relationship after only a couple months.

she has hooked up with men in the past, she says it usually happens when she hasn’t had sex in a long time and is blackout drunk.

So she warned you this would happen. You should learn to believe people when they tell you about themselves.

She then feels gross for weeks afterwards

That sounds like something she tells her lesbian girlfriends because it's what they'd want to hear.

f it had been a woman, I’d breakup with her immediately. But because it’s a man and I know it’s not something she really enjoys, it’s different somehow. But at the same time, you don’t even like it, so wtf?

She likes it. Maybe she only likes it when she's drunk, or the guy has to have some specific characteristics, but there's somehting she likes about it.

This would be like saying you don't want to be with a smoker, and your girlfriend isn't a smoker because she only likes to smoke when she's drinking. Except she's an alcoholic so.....