Yes, you did the right thing. Your ex is not hopeless; it took my first husband a few tries before he got sober at age 21. He finally did, though, and he's now been sober 37 years. I know many similar stories. But it's a path she can and should walk alone. You sound like you've been very supportive and encouraging, but ultimately the secret to sobriety lies within. And there's no reason you should have to continue to suffer while she works this out.
For some alcoholics the losses have to add up to a certain critical mass before real surrender and change is possible. You don't need to stick around for that.
Just sending you a hug. For a "kid" you have shown very mature judgment.