Hi @slipperyslope22, I'm an alcoholic and have been in recovery for around 8 years now. When I first started treatment, a couple of my friends came to me and said "I was worried about you - I knew you were driving the kids to Nursery in the morning and you'd drunk a bottle of vodka the night before and I worried you'd be over the limit..."
I absolutely take responsibility for my drinking, no one forced it down my neck, but as far as I was concerned - no one else had a clue. It was clear from these comments that I was wrong and I do wonder, if one of these friends had turned up at my house one morning and confronted me, and forced me to confess to how much I'd had to drink the day before, then I might have found my way into treatment earlier - it certainly would have meant I would have started walking the children places when I was hungover in the mornings, at the very least.
However, it was not their responsibility, of course. It was all down to me and I just wasn't ready to admit - even to myself - how bad things had become.
With the benefit of hindsight, I know now what I would do in your shoes. I would speak to her, one to one, and let her know that you've noticed that she's drinking more than usual and you've been concerned that she might have been drink-driving on a couple of recent occasions. I would offer her whatever support she needs - finding support groups, speaking to her GP etc. then lay on the line that if she ever drinks and drives again, you will report her, without hesitation. I would tell her that I would expect her to do me the same kindness, as I am essentially trying to keep her and her children (and other road users) safe. She would be left in no doubt that I am serious about reporting her. I might even offer that if she's had a drink and needs to go somewhere, then I'd give her a lift.
Of course, only you know how well this might go over with her. It may damage your friendship forever, it may lead her to drinking more (which would not be your fault - although she would likely frame it that way) or she might pour the rest of the alcohol in the house down the drain and never touch another drop. You just don't know. The alternative is to report her now and hope that the Police stop her on a spot check, but I would hope that speaking to her now might knock the drink-driving on the head immediately.
This is just what I would do, as I think it's something I would have been shocked by enough to properly think about what I had been doing, rather than continuing to kid myself that because I'd slept for 7 hours, drunk a litre of water, 2 coffees and had a bacon sandwich, I'd be fine.
The one this I don't think you can do, is nothing.