@jaxsn Many years ago (before mobile sex pics), when I was 17, I was in a relationship with a girl who was the quiet, shy, innocent type.
One day, she asked me to help act out her rape fantasy. Despite this being in my bedroom, she wanted to role play that she was walking in a park and I was to grab her from behind and play some rapist role.
I was extremely uncomfortable and felt very concerned about her mental state. There were certainly a lot of questions running through my head that I wouldn't never ask her...
I managed to wriggle out of this request, turning it into regular sex instead, but there were enough alarm bells for me to split up with her shortly afterwards.
Your son did the right thing to drop her as you just don't know the kind of mayhem his ex-gf could cause if he'd ever got involved in her 'thing' - especially at the age you're talking about.