It is indeed that the Old Madam has been in power for so long, pampered by others, that she's started to see herself as above anyone else.
Moreover, the fact that Miss Gu could discern the Old Madam's disdain from a mere invitation, and thus chose not to attend, shows her insightfulness. Without some insight, how could she have detected the problem with the invitation?
Nanny Chen is not senile yet; she knows full well who is at fault in this matter, but she is a servant of Old Madam Qi, and has done well in life thanks to Old Madam Qi. She can't afford to offend her, so she did not point out the mistake directly, but instead said, "Miss, in my opinion, let's put this matter aside for now, lest the Second Young Master finds out and becomes displeased with you."
