An invitation declined

An original fiction passage set in the nineteenth century.

Lady Fenwick placed the invitation on the mantelpiece, where every caller might see its expensive paper. She told her niece that she had little taste for crowded rooms and had never enjoyed dancing. Yet she returned to the card three times before luncheon, smoothing its edge with one finger. When the servant asked whether an answer should be sent, she said there was no hurry. Her indifference required a surprising amount of attention.

Identify the sentence which suggests that Lady Fenwick’s lack of interest is only apparent.