Some of the more liberal (and like I said, I'm pretty liberal) posts here remind me of the way my mum parented me as a teen.
In her day, 15yos drank. But they drank at the back of the pub - a pint or two of probably quite weak cider. There was a lot of blind eye turning - according to her the village policeman included - and most of all, they were safe. So when I was that age, she gave me a long leash.
The difference was of course that by 1985, and living in a city, we were necking silly amounts of cheap, strong booze sold to us by unscrupulous shopkeepers (rather than the friendly village landlady who'd tell your mum if you were out of order). We put ourselves in all sorts of ridiculous, risky situations.
I'm still friends with many of my peers and we're all slightly astounded by our parents' naiveté.
It's not really the sexual element that the OP (or anyone else) should be concerned about - it's the ease and speed with which a teenage girl could find herself horribly humiliated, thanks to the technology that simply didn't exist 30 years ago. We need to amend our parenting to take this into account.
The humiliation/embarrasment this girls is experiencing at the hands of her and her BF's parents is trifling compared to what could have happened if (when?) this photo got into the wrong hands.