You should first look at this from an objective adult perceptive instead of looking at it emotionally as the neighbor you don't like.
You don't know what you don't know. I can say my neighbor is a drunk and a horrible mom but that doesn't mean I am telling the truth because I am not in their house 24/7 to know the situation.
Also, TX is a state where a teen aged 14 can obtain a hardship license.
Do you KNOW this teen is driving with no license at all?
I do agree that the teen needs to be a insured driver on the car. You could question the non-ER police division regarding that issue.
As for potential revenge and basic security.... get a security camera. We have security cameras on our property. You don't have to spend a ton of $$$ on a basic camera, especially night vision one. You can get a basic night vision only at Academy for less than $100.
Lastly, as or your daughter. Praise her for following the rules and in reality.... life is not always fair. Like you... she does not know the full story either. Sometimes it is good to give someone the benefit of the doubt instead of spewing hate. Maybe your neighbors are misunderstood. There are so many things that could be effecting them right now that others are not aware of.
Maybe you could get to know your neighbors.
YES, I would concerned but also, I would keep in mind that there are all types of situations and that teen could have a hardship license. If what you say is true, I really feel for the teen and other members of that family.