Like, it is not unexpected for a teenaged queen with cosmic powers to be a bit arrogant or proud. But Egwene at this point is still a country bumpkin who knows a couple of tricks.
Egwene didn't need a taste of power, when she grew up in relative privilege.
Exactly. One of the biggest problems is that no one ever slapped her down for being nasty. The way she treated her sister was abhorrent, but it was indicative of how she treats others when they don't kiss her spoiled little behind. A psychologist would have a field day with this narcissistic little bitch.
The fact that she automatically assumes that any comment directed at her is a slight (unless, of course, whoever is speaking defers to her and worships her greatness) is a classic example of projecting, because her first reaction to anyone not kissing her ass is verbal attack or condescension. It's clear that everyone around her indulged her too much, allowed her to think she was the "smartest evah" and always correct, and never taught her that, in the real world, she couldn't treat people like garbage and expect all of them to take it without retaliation.
Her parents, as well as everyone in the Two Rivers (and, while we're at it, at the White Tower and with the Aiel), did her a great disservice by not crushing her arrogance. If she hadn't died during TG, the world would've been in deep trouble with her running the WT. The Seanchan ways wouldn't have looked so bad after a couple of years dealing with an Amyrlin Egwene who had no checks or balances on her.