A complement is part of the nucleus of the sentence and can't be removed.
I present a car to my sister, brand new. -- With a comma preceding 'brand new', this is very loose colloquial style at best.
In this sentence, in my opinion, there is an example of reinforcement, a feature of colloquial style, resorted to for purposes of emphasis. An amplificatory noun phrase is added at the end of the sentence, part of whose words is ellipted.
I present a car to my sister, (a) brand new (car).
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