Sense Of Entitlement
Having to interact with the wealthy children in your class is challenging in and of itself. But things take a completely different turn when their parents get involved in the situation. There are times when these children have a sense of entitlement not only due to their wealth but also due to the behavior of their parents.
In the case of this grandmother, that is precisely what transpired. But in all honesty, it was deserved, and I imagine it must have felt pretty darn good for the original poster. Sure, it was a little inappropriate for this child to talk to an adult in that manner.