Can a 17-yeat-old victim of sexual assault sue the family of her 16 year-old attacker even when the police drop the charges?

There are two basic things to consider, in looking at a possible lawsuit.  One is liability, whether the potential defendant can be held legally responsible for what happened.  The second is damages, which is the amount that could be recovered.

I'm not a Texas attorney, so you should talk to someone who does personal injury practice in the state, about whether the parents could be made to pay for what their son did, just because he's their son, because my research doesn't show any statute that would make that happen.  Otherwise, as MTD said, you'd have to show that the parents had some reason to believe their son would do something like this, and they didn't do what reasonable parents would have done to prevent it.  Otherwise, you're just going to be suing the child, who probably has very little if any money of his own.

The damages are the other consideration.  How badly was the girl traumatized?  Has she had to get counseling or therapy to get over this?  Is it worth making the girl re-live this incident, probably at least twice, at a deposition (pre-trial interview under oath) and at trial?

This leads to a third problem: how do you prove your side of the story?  From the fact that the police talked to both of them and dropped the case, you can be pretty sure of two things.  One is that there were no witnesses.  The other is that this is a he-said-vs.-she-said case, and the boy certainly did not simply confess.  He either said that he didn't do it, or he said something like the girl did it voluntarily, but then got mad at him for some other reason.  The girl will have to answer questions about what happened, questions that will at least suggest that she was at least partly to blame somehow for what happened.  I don't like this, but the system has to make both sides face cross-examination, to get at the truth.

The choice by the prosecutor to file criminal charges is different than a person's individual right to sue.  In terms of dropping charges, was that the police or prosecutor? Call the D.A.'s (district attorney) office to talk to them about this.  Oftentimes, you will find the D.A'.s office may decide to charge.  google for Texas , then the county, then D.A.

In terms of private suit, contact www.attorneypages.com, the Texas State Bar or legal aid to find a lawyer to personally sue the child and possibly the family (the parents if this individual has a history of sexual assault and/or driving issues and parents allowed him to keep acting in this manner).