I'm sure someone in stage 4 cancer, for example, would be delighted to have had an opportunity at stage 1 to take stock/have a firm word in the mirror and make lifestyle changes to arrest its progress
It's not a very palatable thing to say, but there is a significant lifestyle component in lots of cancers, lung cancer being the most obvious, but lots of the others such as bowel and stomach cancer are linked to obesity, diet, lack of exercise and, ironically, alcohol consumption, even at very moderate levels. Even when you get breast cancer, some people's outcomes are better if they exercise.
I find this research quite controversial, some of this may be correlational (the people who were the most able to exercise may have then had the best outcomes) but there can be finger-pointing in many diseases if you go down that route, even dementia.
Finger-pointing doesn't help anyone.
For what it's worth, neurobiological models suggest that the brain is altered by repeated exposure to drugs and alcohol. That might mean that the person doesn't need to use every day, but when they do use, their use is compulsive, out of control and detrimental to all around them.
Binge-drinking is incredibly risky and can easily result in early death, as I'm sure you know OP and your mum also knows. You have to ask yourself, if it is just a matter of her 'choice', then why would she risk an early death?
I don't believe your mum has the same 'choice' over drinking as I do, to be honest, she's probably developed a binge-drinking disorder over time and is at risk every time she binges.
This is very sad, and not your fault, and you are right to feel angry, but she isn't 'choosing alcohol' over you, her brain is now finely attuned to alcohol through both habit and neurological changes, and it may well take her to an early grave. That isn't incompatible with enjoyment of course, she may enjoy herself when she drinks but that doesn't mean she can choose easily to stop.