Curiosity is a NATURAL human trait
I recommend that you suggest to your son and daughter to chat to see if this past event is of any concern to HER.
A pschologist does NOT need to be told !
You seem to be leaping to a lot of conclusions ..... that this curious looking has caused her current state and some ALL KNOWING authority needs to be notified.
You state:
It is years later, but my daughter is showing signs of typical molestation victims: listlessness, authority problems, solitude.
IT Does NOT sound like your daughter was molested in any way.
Your daugher's symptoms can be caused by a MULTITUDE of things. She probably is also magnesium deficient since anywhere from 50 to 85 % of people are and THAT CAN cause the problems you listed.
Also introversion is not a disease.
IT is NOT a slightly abnormal thing for children to look at, or be curious about each other's bodies. It is perhaps erroneous to believe that natural harmless looking and curiosity is a Bad thing.
Why would YOU want to bring this to a pyschologist ?!
I strongly suggest that you consider researching other reasons for your daughter's signs. You also did not state enough about the nature and severity of them for anyone to give very helpful suggestions.