There are other people, who need you, in your life
If there are additional children, especially still in the home, don’t force them to live their lives constantly in the shadow of their sibling’s actions. Yes, you are brokenhearted, but your youngest child’s birthday is coming up, and she deserves a celebration.
The prodigal son of Jesus’ story physically left, and while his father never stopped looking for his return, he also didn’t stop living his own life. He had a farm to run, and at least one other child.
It’s a toss-up whether it’s easier to have the prodigal out of sight and far away, or near enough that you are constantly updated as to the latest scrape, but either way, there’s not much you can do for someone who isn’t listening and doesn’t want to change direction right now. You major activity is to pray.