Please google "Al-Anon" and the name of your state, and you will find links to the meetings in your area.
The meetings last one hour, perhaps 90 minutes for some. You do not have to talk or explain your situation. There is a format which is followed, and members share their experiences of being affected by alcoholism in a friend or a family member, and they relate how they are recovering from those effects, using the Al-Anon program which is modeled after the AA program of recovery.
All you have to do is take a seat and listen and then leave. You can talk to a member after the meeting if you wish to, as it is common for some members to linger afterward or to help put away materials. Or you can simply leave. Nothing at all is required or expected of you, it is a gentle atmosphere, and the sole purpose is to provide solace and education to families of alcoholics and addicts. Everyone there has the same problem.
At every Al-Anon meeting there is an assortment of free pamphlets which explain the disease of alcoholism and describe its impact on the family and give direction to the family about how to cope with alcoholism. You are welcome to take several of these free pamphlets, enough to share with your parents and your fiance, and in doing so, you will be the first member of your family to face the reality of addiction in your midst and to start recovery. It is a family disease, and it makes all involved emotionally ill.
Your grandmother is an alcoholic because she carries the gene for addiction. At some point in her drinking life, her brain underwent a change, the change was silent and invisible to all, but at some point, in years past, her brain became the brain of an alcoholic.
The gene is in your family line and it is also in your fiance's family line. Addiction is going to continue to show up, in some members but not all, for generations to come. But there is a world of difference in the outcome for the family once recovery starts happening. The cycle of denial and despair does not continue like an endless loop. When one of you--when YOU--start recovery, then you change the entire dynamic of the disease within your family, present and future.
Welcome to SR. I hope you will continue your journey toward awareness. Your grandmother will be best served by people who set firm boundaries with her about what they will or will not cooperate with. As your recovery progresses, you will become more and more clear about the right action.
When the family refuses to enable, your grandmother may walk back into the rooms of AA.
If she never does, if she dies an alcoholic, your family -- because of recovery --will be spared much of the guilt and anguish you might otherwise suffer if you thought you might have been able, in some way, to stop her from drinking or to save her from it. You are all powerless over the alcoholic. Al-Anon can teach you how to cope with that.