Or she could be the product of years of psychotherapy.
Speculation about incest is just as bad as assuming that she was a slut.
It doesn't have to be a family member, though that's the usual explanation. It could have been someone else.
But notice, I say I'm speculating. I say I don't know for sure. Starting rumors without evidence and presenting them as fact is worse.
But why was she in therapy, and why is she the way she is - squeaky little girl voice and nervous mannerisms?
I'm not a mental health professional, but (assuming it's not all a put-on or a reaction to having to testify) those can be signs that someone was deeply damaged early on in life.
Childhood abuse is a possibility, and investigators usually start looking within the family.
If I said she had been a victim of incest and left it at that, I was wrong - incest would limit the suspects to a few names and they might all be innocent.
But I don't think I was wrong to mention the possibility that she was abused, and I still think that line of speculation is not just less objectionable, but more relevant and more to the point than going down the nutty nympho slut route.