I think Nellie is naturally willful,my ds was quite capable of throwing a strop that would make Nellie's pale into insignificance when he was her age and that was without all the materialism. There was no talking to him,he just had to get over it in his own time.
I doubt Nellie behaves like that at school in part because she will have clear boundaries and isn't being made to parade around in designer clothes when she's had enough and is tired.
Billie's comment about the sea in Spain not being like the sea in Maldives 