There is only one type of alcoholism, the addiction to the rush of pleasure felt soon after drinking alcohol. After that fairly brief moment it is pretty much all downhill. This shows how on such a short term level the human mind works. Almost all we do is driven by short term gain.
There are, though, many causes of alcoholism, meaning the reason for arriving at the position at which one is addicted to alcohol.
One of the reasons for Jane is that she dislikes herself. This emotion about oneself will, it is certain, make life almost impossible to live. It is tough enough living in the world we have built but to dislike oneself at the same time - forget it.
Her dislike of herself leads to the desire to punish herself. In my opinion she has been trained by her parents to be punished for being naughty. She is punishing herself by drinking neat Vodka. She knows that this will hurt her. She doesn't even like the stuff.
She knows that it will cause upset and that will lead to me being annoyed so once again she will be punished by me so she thinks - actually I don't punish her. Obviously to punish her is wrong but I think in her mind she is being naughty again as she was to her parents as a child and expects punishment as a result. This is a form of self harm (call it indirect self harm)
Jane still acts like a naughty girl, behaving like a young girl sometimes rather than a fifty plus year old women. She is time locked in her naughty girl phase.
Self harm photo copyright tinkernoonoo - the person depicted is no Jane