I remember once as a youth myself when living in the UK and i was 13 and i was travelling from UK to Orlando to visit my best freind, it was also a service that was paid for and i flew with British Caledonian,
my parents paid extra and the service was 2nd to none, they took me from my parents and handed me over to my freinds relatives in the US!
So in my opinion there is no defence really for KLM, i can only sympathise with you for their actions and you should be proud that you have a daughter that can look after herself given the situation she found herself in!
cheers