Hi, JP! What do you mean by a "fit?" A seizure or just acting aggressive and explosive? In either case, it's most certainly caused by her alcoholism. If a seizure, it could be from alcohol withdrawal. They should be giving her a tranquilizer while she withdraws. If behavioral, probably hepatic encephalopathy as Mer suggested. In either case, it's going to get a lot worse if she doesn't stop drinking.
Very good suggestions, Arneeb. You cannot persuade her to stop drinking...she has to come to that decision herself, and it seems she has decided to continue drinking. As a sober alcoholic, it makes me angry, too, But I also know that nothing and no one could've made me stop drinking until I was ready. She is unable to imagine "living life on life's terms" without the buffer of alcohol. What she doesn't realize is that she is making matters worse, not better. Living life sober is a terrifying thing for an alcoholic--and why they need help from a program like AA.
If you can get her to make out a Living Will (if she doesn't already have one) and to express her preferences regarding cremation or burial, etc., it will prevent a lot of hassle and heartbreak when the end comes.