I have friends who are all over the drinking spectrum, a few of whom are currently doing some self-reflection on their own habits.
I talk about my ongoing experience every once in a while, and I answer direct questions they ask me, but that's the line for me. When they talk about drinking I don't give advice or opinion.
I do this for a lot of reasons, including not knowing for sure whether they have a problem or not. But the most important reason is that when it comes down to it, their drinking or not won't affect my behavior until they're either putting themselves or me at immediate risk. Like you and your friend, it won't change things between us right now.
That being the case, I try to let their process be entirely their own so that our relationship doesn't have to be thrown into uncertainty as their thoughts about alcohol change.
I think there's a reason a lot of us choose to get our support from this website and other groups of people outside of our daily life. I feel like anything that gets too close to the alcohol in our lives risks going up in flames the next time someone drops a match, you know? I like to keep it as far as possible from the people I care about as long as I have the luxury to do so.
All this is to say I think you should be light-handed with her. Let her know you're there and that if she needs anything you'll be there, but then let go and trust that if she needs support she'll find it. The text message seems like a great approach, super low key. From you she needs primarily your friendship, and it sounds like you're already a really good friend to her.