This is totally rude. I'd take your 13 year old, I know the principal of the matter is that you bought the ticket in good faith on her behalf and she hasn't paid you for it, which is totally inconsiderate.

I have a "friend" that I leant $300 to before Christmas so she could pay her rent (she works casual and had been sick), we're now in August and I've still not seen a cent of it, yet she can afford to take her kids on holiday, go out drinking, get a new phone......