That must have been an unpleasant experience overall, and that stinks.
Were you booked in J initially? Was your daughter in Y? Was this an award or a paid itin?
Believing that they will "try" to UG your daughter is a bit naive, IMO. I never buy that kind of stuff. It's just to get you to cool off and hang up.
Is the voucher what you would be owed under EC 261 rules? What was the cause of the delay?