Hi and
to SR!
Just wanted to pop in a post the 3 C's of alcoholism for you:
You didn't cause the drinking
You can't cure the drinking
You can't
control the drinking
Her drinking is entirely her choice and nothing you say/do will change that. You can inform her that you have a problem with this secrecy but beyond that, don't expect that pouring the booze out, sitting her down for "a talk" or any of those other strategies, is going to work.
If I were you, I'd seriously think about putting off the wedding until you have decided what you're going to do about this issue.