You have already mentioned several causes of your mother's symptoms. She had a significant stroke 4 years ago but has likely had ministrokes as well. This plus extended alcohol use will causes a form of dementia and this is a cause for behavioural change including loss of appetite. Also, depression is common post stroke and also with alcohol excess and this can easily cause appetite loss.

You need to know what the brain looks like. If there is a "multi-infarct"picture on the mri and a lot of "atrophy" from alcohol excess, this behaviour may not be reversible and could progress. She needs any depression to be formally diagnosed and optimally treated as well though.