Hello Archiebald, it's not so much spying on her, although that's what it seems to be for her, it's your concern on why she needs to do this behind your back and be a cupboard drinker.
I was also one of these drinkers when suffering from depression and didn't like any of my family searching hiding places, but now know it was out of concern as they weren't sure why I had to drink behind their back, but with my depression, no one seems to understand unless you're a trained professional.
One drink to others is one too many and not addressing the cause but more so the action, 'you don't need another drink', that's why the alcohol is hidden we don't have to try and justify why.
The only person who can decide to stop is the person who is drinking because any demands or 'pretty please' won't necessarily be enough to achieve this and if the person wants to open up and say why they drink will normally be disagreed with.
Drinking may not mean there is a problem with the marriage but it may appear to the person who is watching this to be the case, but the reason why needs to be investigated by a professional.
Someone in this position holds their reasons close to their heart because deep down there are reasons why this has happened and the alcohol seems to numb their feelings.
I'd really like to continue this later on as I have something to do, I'm sorry, but will certainly get back to you, early in the morning.
In hindsight, I understand your concern as I haven't had a drink for over two years.