I am shocked when I see films where kids are sleeping together with parental approval and they have drug parties where parents are not present.
The father of the boy, her parents, and her friends leave it up to this young inexperienced girl to take care of Sebastien until they see a bit of what is happening. By then it is too late. The prosecutor is heartless toward this young girl and looks at her one dimensionally and not as a young girl out of her depth.
That aside, this is sad and as it goes along it is hard to watch the unfolding of a tragedy.