The context describes being upset or horrified at having to miss an important family event (a son's wedding). 'Appalled' means shocked, horrified, or deeply distressed - which perfectly matches the emotional intensity of missing such a significant occasion. 'Apt' means suitable or likely, 'amiss' means wrong, 'ample' means plentiful, and 'apparent' means obvious - none of which capture the strong negative emotion required here.