Happy's exactly right.... this is a personal decision that you need to make for you & your family's best interests. It's OK whenever you say it's OK. It feels dramatic because it IS, but that doesn't make it over-the-top or wrong.
I, for one, have zero problems putting my kid's mental health & welfare before that of an active addict, no matter how minimally she is impacted by their behaviors. And I also have no problem saying it precisely like that - DD comes first, you are an adult who has the ability to make better decisions.
It seems from your join date/original post way back then, that you have been dealing with this for a very long time & I'm sure you're seeing a progression with the disease. ((((hugs))))