Just a thought about Facebook. If this is something where there is likely to be Press interest, please advise your dd and her friends to make the Facebook page private. (I've never used Facebook, so don't know how to do this, but I know it can be done.) When someone I know died in tragic circumstances a year or so ago [don't want to say too much on here but it was a big news story at the time], the Press were raiding the Facebook pages of her friends for juicy quotes about her and young people who were already terribly terribly hurt were finding what they thought of as their private messages to their friend splashed all over the tabloids (sometimes attributed, sometimes not). It was very sad, and just added insult to injury, really. Sorry to put a downer on the Facebook thing...
MABS I am so sorry for your dd and her friends and all those involved. IME, young people (the ones I work with a a bit older than your dd, but even so...) are very good at 'being there' for one another. I've been very very impressed by how the people I've been involved with have supported one another, both in the immediate aftermath of what happened and in the longer term. Encourage counselling if they feel it will help, but bear in mind that they might not feel they need it now but might want to talk later. This has happened with the people I work with... a year on, some have come forward and said 'I don't feel I can keep on going over and over what happened with my friends after all this time' and have found counselling helpful at this stage as a place where it's 'OK' to talk about what happened.
I am so sorry, and am sending you much love.