David, I am not the moderator of this forum but I do know that thoughts of suicide are not allowed here. So please do not make such comments. I have read you post several times. This girl is treating you terribly and I assume she has for some time. My question is why do you want to be with a person who behaves this way? In addition to all the bad things she does to you, you are saying that she has problems with alcohol. Blacking out from drinking is extremely serious and one does not black out from one drink. Is it possible she takes meds or drugs in addition to the drinking? A person who blacks out would be considered an alcoholic. You just got engaged to her, why?
She is going to need some intensive help if she is going to get better and become a kind and loving person that you would want to marry. Marriage is not going to change her so don't think that once you are married things will be different. They will only get worse.
You may love her but right now she is toxic for you. Why do you put up with such behavior? How did she manage to get you to put a ring on her? You have a lot of questions to ask yourself. Don't consider marriage at this point. You need to find out why she behaves the way she does. This is an abusive relationship. I would run the other way. Love is not going to help you and if she loves you why would she treat you so badly?
Also, I wonder how old both of you are. Don't do anything in haste that you will have to regret for years. It is easier to break an engagement than to get out of a marriage. I know this probably sounds harsh to you but I am seeing your situation from a neutral point of view.
Please write more and give us more information. We may be able to help you in a better way if you tell everything that is going on.