Actually, if you really want to be fair to the police,
1. She was pulled over for violating a traffic law. This, by the way, did not violate the United States Constitution.
2. She was cited for underage possession of tobacco which, apparently, constitutes a violation of a State or Municipal statute.
Did she give the police permission to search? Even if she didn't, the police probably had the right to search the interior of the car for additional contraband (tobacco).
Don't like the law prohibiting the possession of tobacco by minors? Well, don't blame the police, who appear to have simply enforced the law. Blame the legislature (which enacted the law).
Then again, you could still hire a lawyer, and sue everyone (especially that horrible police officer).
I hope that things work out O.K. for your Niece. But I just can't see blaming the police for enforcing the law. Personally, I'd just tell her to avoid driving there while she is speeding and/or smoking.