** spoiler ** Isabelle solo scene
Before Isabelle loses her virginity (and I think this was planned to be with 'whomever' came along), Victor opens the bedroom door to see her masturbating.
This scene was more erotic than any other sex scene in the movie.
O.K., maybe I'm biased because I do it the same way. (It was nice to know that others find this such a 'facilitating' position.) ;-)