"B00, but as I understand it, the invitation was initially accepted, therefore she would have booked and paid for his place anyway. "
Yes, but I was trying to say was that if she's known beforehand he wasn't going to come, she wouldn't have booked his place (obviously-lol) thus saving the money.
Yes I do believe she's making a bit of an burk of herself over it, too OTT in her outrage and reaction, however I myself would be peed off if it was my child's party and I'd paid for an absentee.