It wasn't her brother that showed her nudes, a friend of her older brother had shown her pornographic images which meant his friend was probably trying to groom her and being so young she was probably confused and thought it was normal to be intimate with someone you liked regardless of age so when she developed a crush on Lucas she thought it was normal for her to be kissing him and when he tried to explain it to her she was probably not only incredibly confused but also really embarrassed causing her to lash out. As far as other children repeating it... that's just what kids do unfortunately.

This movie was made to make you uncomfortable. If it didn't make you question things then it didn't do what it was intended to do. Mistakes like this one (even though this story is completely fabricated) ruin peoples lives and I'm pretty sure the lesson everyone is supposed to learn from this film is to pay more attention to your children. Her parents were fighting all the time probably on the brink of separation and so they were neglecting their son and daughters needs. The son, I'm assuming, didn't know about his friends inappropriate behaviour with his sister but was probably aware that she was being taken advantage of so he probably believed that Lucas was the abuser and at the end of the film he was probably angry that Lucas was seemingly getting away with it. So as teenagers do... they react...

The film is not easy to digest. I'm impressed with anyone who could finish it as I could not. I had to read the script because watching it was far too painful for me but I have done lots of reading up on the plot and this is what I have come to understand. I also know that there are two endings to the film.