A "friend of a friend" is maybe getting distant enough so that it's not really about this particular person, but about an imagined person - you heard the story, and you imagined how it would be if it happened to yourself. It could just as well have been something you read in the paper or in a book, so I can't see that privacy issue scome into it.

This is a tragedy that happens in a lot of people's lives. In any audience there is almost bound to be someone who has been touched by it, so you need to be sensitive about it, but that doesn't mean nkt singing it.