Devil's advocate here, and yeah it might be a long shot, but how do we know her BF doesn't give a shit if she fucks some randoms? I know a few people like this. "He would be really shocked", is the understatement of the century if he were your typical dude.
This sort of thing affects people differently. It wasn't until many years later that I'd realized having sex with an adult when I was 14-15 probably messed me up in some ways. They groom you, and it's a plenty creepy looking back on it now knowing how predators behave.
