She may have deep-seated issues from childhood around this, and there may also be self-esteem/self-consciousness and trust issues as well. Many folks with religious upbringings are led to believe oral sex is dirty and/or unnatural.
I was like this... I had a mental blockage every time he tried to go there, all I kept thinking was "ewwww how can he stand that, my brain could not allow me to enjoy this act... I remember it feeling ultra sensitive also... it was "dirty" in my head , I associated it with porn... I always used to push him away not long after....
It helped to get a sexual education, reading secular books written by sex therapists and an uptake in my sex drive -that was the end of my inhibitions. Now I would be upset if he didn't want that part of me.
If she likes it when she is drunk, she has to be self conscious the way I was, feeling it is dirty/wrong/ or something.
Here is something my husband never did .... which I think looking back, it might have helped me... He was never one to talk during sex, or tell me what he wants to do, seductively flirting with me kinda thing... or go on about how much he loves it, how it makes him feel... it was just always "silence" -which allowed my head to scream "dirty". I would think this would be very erotic and if she has a mental blockage, all this verbal reassurance
could help her....maybe ease some of those inhibitions.
I don't know, those are my thoughts.