Al-Anon is for people who are connected to someone with a drinking problem - a spouse, an ex-spouse, a parent, a kid, whoever. It's similar in form to AA, except that the focus is on how to look after yourself while you navigate the challenges of dealing with a problem drinker. There's a lot of emphasis on detaching (in a positive sense) and understanding the limits of your action, as distinct from trying to get someone else to stop drinking (which is pretty much impossible). I've found it very helpful. You can go to Al Anon even if the problem drinker (the "qualifier") is not going to AA and/or is still drinking heavily.
I don't know if your wife is technically an alcoholic, but it sounds like her drinking is a problem, whatever label you want to put on it. The hiding and the defensiveness when you bring up her drinking are yellow flags, if not a red ones. It sounds like she doesn't want to you to know how much she drinks and she doesn't want to even consider the possibility of drinking less. Al Anon can help you stay more or less sane while you seek to understand this difficult situation and think about your options.