I have not followed the story a lot but from what I have read and heard about her case, I'm not sure if she actually molested her younger sister. Therefore if there isn't enough proof for me, I can't say that she did it, as I can't say she didn't do it. We will just have to wait until more evidence comes out.
I am not a fan of Lena Dunham, not because she isn't talented, but just because I just don't like her. Having said that, there is nothing in these stories that suggest sexual molestation. Little kids don't know enough to do such things, and attacks such as this one on Lena Dunham are nothing more than gossip fodder.
Lena Dunham did not sexually molest her younger sister. Lena writes about seeing her younger sister's vagina at the age of seven and how she tried to persuade her to kiss her in a way that "a sexual predator might do". At the age of seven, being curious is ordinary and although written in comparison to a sexual predator, I do believe the statement was humorous and not literal.
No, I do not believe Lena Dunham sexually molested her younger sister. Lena Dunham is a shock-style person, and I believe most of what she wrote in her book was simply that. A way to shock the public, and get them talking about her. I would hope that if it actually did happen, she would be addressed in a legal manor.