Answer:
Encourage the behaviour and make her believe that this is the way to manage what she wants.
Step-by-step explanation:
Right now Deirdre is very young now so her tantrums are manageable and her parents are in a better physical position to handle it. As she gets older she will understand that whenever she wants something she must use aggression and she must defy her parents in order to get it.
As she moves into her school years this behaviour will be continued with the individuals that will tolerate it.
Later she will also learn that there are persons where she can continue this behaviour and persons that do not tolerate it. She will act accordingly.