The child support will remain payable by your ex to you until age 21 or until a court modifies it.
Either you, your ex, or the child can ask the court to stop the support, but it never happens automatically. And it is never paid directly to the child.
In your case, the grounds for terminating the child support would be that your child is economically independent of both of you. But just because she moved to her own apartment does not necessarily mean that she is economically independent of her parents. If either of you would be giving her money, or buying her groceries, or putting gas in her car, etc., she is not economically independent and the child support would coninue to be paid by your ex to you.
I hope this answers your question. If there is anything that you do not understand, please let me know and I will be happy to explain further.
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P.S. I am frequently asked how someone can specifically request that I, personally, answer a question. Here’s how: for new questions in the future, always begin your question with “QUESTION FOR THE JUDGE.”