oh dear poor you tess. I just wanted to give my support as well.
I totally agree that people abdicate responsibility to the nearest broad shoulders, and will continue to do so until those shoulders shrug... so heartily relieved you are going away for a couple of days. well done you. Its the best thing you could do, for yourself, and also for them too.
Just wanted to say on the subject of sex for dares... My job involves looking at youth trends, and there has been a big trend in recent years towards sex as really rather childish play, not sex as we adults see it.
Please try and not let this totally shake your idea of who your DSD is, she lives in a world where these things are seen as 'fun' & exploring physicality and their changing bodies, and not seedy and awful.
When we look at these things they feel very un-innocent and horrific, but they tend not to be doing these things with the same motivations and connotations that we see.
'Lipstick parties' are far too common (where each girl wears different coloured lipstick & goes down on a boy so he's left with a rainbow of different coloured lipstick on his penis). It makes it a game, and allows them to experiment with a feeling of belonging and with their peers (not to mention the risque / daring / egging each other on thing)
Girls often choose to lose their virginity with a friend, as it seems like scary than mixing it up with proper feelings for a boy... Its just a shame they can't reduce the consequences to a silly prank as well.
I can so imagine a rather studious girl with not much of a sense of self esteem/ wanting to be loved/ accepted, thinking in the heat of the moment, with peers all validating her, and with a boy she didnt regard as threatening... ending up having sex like this. Poor her (poor you most of all though...)
I am not saying any of this is right (indeed I think its bloody awful personally), but I hope it sheds a different perspective on her environment and motivations for things that seem almost inconceivable.
good luck and I'll keep reading, my heart goes out to you.