In a "Christmas Memory" by Truman Capote, why does Buddy´s cousin spend the evening in tears?

In Truman Capote’s “A Christmas Memory,” Buddy’s cousin spends the evening in tears after relatives find the pair drinking a small bit of leftover whiskey from making the fruitcakes. As they are chastised, she blames herself for their transgression. Her age would indicate that she would know it is inappropriate to give whiskey to a seven-year-old boy, but her lack of adult judgement is apparent. "It's because," she hiccups, "I am too old. Old and funny." In this case, funny means that she is limited by the disabilities she acquired from a youthful illness. Buddy attempts to comfort her as she cries and cries long after the others have gone to bed. He tries to tell her that she is not “funny” but that she is fun. He also reminds her that if she continues to cry she will not be up to the task of cutting down their Christmas tree the next day. In this case, the seven-year-old boy acts as the adult.