I do love her, and don't want to intentionally cause damage.
Say what you mean, mean what you say, but don't say it mean. Reality bites. You going to AlAnon is a consequence of your loving an A (and perhaps even from stuff you learned in your shildhood w/ an A stepgfather!!). I mean, it is just the reality and of course she will, like every active A I've ever known, blow up and try to argue with you about whether or not she even has a problem!! (Get ready for the "I can cut down" promises or the "how dare you imply that I am an alcoholic!").
Try not to engage in the argument. As calmly as you can say "I am exploring AlAnon for me. I need help dealing with the repercussions of people's drinking on my life. It's for ME, it's my business."
Of course she knows she has a problem. But it is the nature of addiction that if she can keep denying it to the world and defending herself she doesn't have to face it herself.
You don't have to say anything hurtful. The trick is to truly keep the focus on yourself. Not easy but worth it.
Peace-
B