Saying that you're letting go and leaving her to lead her own way sounds like positive supportive stuff. You didn't call her names or insult her character.
yes, I don't think everything I say to people is "perfect". Maybe I should have added this, and maybe added that - ooh, I would have changed this thing I did. I know the feeling of second-guessing your actions - I do it too! I still do. I work to be happy with my imperfect not saying the right things all the time person.
Even if I was perfect and eloquent with my statements, my father will still drink. My brother will stay say horrible stuff about my wife. I will still have to walk away to protect myself.
Also note that other people in my life - ya know, the program people, the supporters, the people that FEEL like family every step of the way. They forgive my faubles and mistakes almost instantly. They understand and give me room to breathe. I don't have to be perfect to earn their love, respect, acceptance, etc. I just have it. Period. end of story.
Follow your gut and your heart in what it tells you. Yes, you probably would have liked to tell her "I love you" as well. But, it's not the lynchpin between sobriety and drinking. Out of your control.
Heck, in a difficult moment with my sibling, I said "I love you and wish you well" -- his response? "I don't love you and you're not my family" and when I said that hurt, the cursing went through "I don't give a f***," curse, curse, curse. My love didn't reach him because...well. HE decided to not accept it. His choice. I'm willing to bet a "I love you" added to your boundary statement wouldn't be the be all and end all of your interactions with your mom. In my personal experience, "I love you" inflamed the person I spoke too. Weird, eh?
Progress not perfection.
Good for you in taking care of your children. My mother has never truly acknowledged my father's drinking. Ever. I would have liked for my Mom to stand up and say, "this is enough." You love your kids too and they are a high priority in your life. Kudos for thinking of their safety!
My heart goes out to you. Wishing you well.