No contact was made to her parents to advise them of the problem? You've written in you post that she was YOUR daughter so didn't you already know the flight was delayed before you passed her to the groundstaff?!!
The issue here is that she unfortunately had a long wait in Chicago which can happen when flights are late and connections are missed. The issue isnt that she did not arrive at her final destination safely, she was badly treated, left unattended or unsupervised or not given the due care which is afforded to unaccompanied minors by airlines when travelling alone.
So your word of warning should be....Delays happen, missing bags happen thats air travel fo you.