I saw a similar situation work itself out with a juvenile serial "I've been molested!" reporter. She was also very precocious in her sexual interests and obsessions and accusations. Keep in mind, there are some sixteen year olds who look like they're twenty five, and their hormones are telling them so, too. Of course, in the long run, it came out that this girl had been molested, just not by all the people whom she had accused of it. And a lot of it had occurred much earlier in her childhood. I agree with everything java said.
We later found out that by this age, she was already having a relationship with a much older boyfriend, though, and kept backdating the occasions of supposed molestation by her uncles, her brother in law, etc. when she feared she was pregnant. Eventually she did age out, her parents found out about the boyfriend, she did become pregnant, many many issues. I suspect that this is a case of, as the OP says, "from what I know about it" and he does not have the whole picture. But surely he understands that all the indignation both about his being accused and the anguish his poor wife has had to endure just makes him look overly concerned and a bit silly and much more possibly guilty than some dignified avoidance would. No you can't sue your in laws for their 16 year old daughter's college fund! And this is what you'd be doing. Shut up, step back, stop making such a huge deal of this after the fact and stay far away from this trouble maker for the next two years. Or for the rest of your life. What she needs (counseling) or deserves (to be sued and have to pay for her troublemaking) will not be your place to decide, ever.