The young woman merely expressed her personal aspirations and preferences when prompted by her uncle, who initiated a comparison between her life and his children's. It's unfair to label her as a 'spoiled brat' for articulating her ambitions, especially when she was put in a position to defend her choices. She didn't maliciously attack her cousins, but rather highlighted the differences in their educational paths and extracurricular activities. The uncle overreacted and should not have involved Katie.
While the young woman is entitled to her opinion, her comments reek of arrogance and condescension towards her cousins and their lifestyle. She deliberately chose to denigrate their homeschooling and lack of extracurriculars, knowing it would wound her uncle, who is proud of his parenting choices. Her 'guilt' is a thinly veiled attempt to absolve herself of responsibility for her thoughtless and hurtful words. She needs to learn that differing opinions don't give her a free pass to be disrespectful.
While the uncle initiated the comparison of lifestyles, the young woman's response was unnecessarily critical and judgmental towards her cousins. She could have expressed her preference for her own life without directly disparaging theirs. The uncle's reaction was excessive, but understandable given the perceived insult to his children. Both parties share some responsibility for the escalation of the conflict, but the young woman was in the wrong.