Chiming in a little late here, but here goes...
I still don’t think AW gets how much the girls have suffered. On the one hand, telling AW the above might cause her to reach for the bottle; on the other hand, this might be more incentive to stay sober and try to undo the damage (provided she accepts that damage has been done).
GiveLove has said it perfectly: Alcoholics have amazing powers of denial.
Your post reminds me of when my mom used to tell my AF that I was upset with him as a teenager. She even told him for me that I felt I couldn't talk to him. He denied it, and even said to my mom that "dothi doesn't have trouble talking to me."
He didn't ask me, of course, because that could have entailed facing the truth.
The few times he and I did get to talking about it, I got a lecture about how much more difficult his life is than mine, so basically I should suck it up and let him drink. To this day he is still very skilled at turning conversations about my feelings (e.g. dad, it really upset me when you drank at [function]) into conversations about how tough his life is (therefore, he deserves to drink). It doesn't matter what I have to address (complain about), because his feelings always take precedence over mine.
My point is that so long as the alcoholic is in denial, they will fabricate/twist/invent reasons for why the drinking isn't the problem. Just like my AF, your AW doesn't want to know that her drinking is damaging her kids. And because they can't stand up to her as adults yet, she'll either laugh it off or assert that they are just kids and don't know what they're talking about. Please don't give your girls the expectation that bringing their pain forward (directly or indirectly through you) will cause that big change you've all been waiting for in mom. It will just let them down.