OP growing up as a child of parents with mental health and alcohol issues is toxic and extremely damaging to the child and sometimes they just need to emotionally disengage for their own wellbeing. They are I am sure understanding of the mental health issues and don't apportion blame, but that doesn't make the situation any less toxic for them and they do have to engage in some self preservation. The holiday I'm sure was just another version of what your daughter has always lived with, just more of the same, and perhaps she needs to disengage to quite rightly prioritise her own mental well-being. It also wasn't just the holiday, I'm sure, it was how it triggered an avalanche of distressing memories for her, too.
The alcohol to self medicate wasn't acceptable, it wasn't the right thing for you to go on the holiday and feel pressured, but the sum total is that yet again your daughter carried the huge mental load of understanding her parents situation with no support for her own mental well-being.
Over time she has probably had to learn to be extremely self sufficient and resilient and walk herself through some hard times growing up as she knew her role was ultimately to be a support to her parents, not to have that normal child role where they support her.
I am sure she loves you very much, and is concerned for how much you suffer with agrophobia, but it's toxic for her. My guess is that she needs to see you move from the self medicating with alcohol, for sure, to a more positive approach, if you want to do something constructive with your relationship with her.