The possible explanations for the kid’s behavior lie on a continuum – at one end is the possibility that she is a spoiled brat who seeks to give her parents and all other loving adults in her life the middle finger.
At the other end of the continuum is the possibility that she is a kind girl who suffers from severe anxiety, complete with crippling panic attacks, and that she’s developed a phobic response toward anything to do with the party, partly out of shame for her own behavior, and that even the thought of the gifts (and thank you notes for the gifts) threatens to send her over the edge.
Most likely, her condition is somewhere in the middle, but based on the limited information provided, it is hard to guess where on the continuum she may lie.
I’m guessing she is pretty far over on the anxiety side of the scale. The spoiled brat would have taken the cash.