Final answer:
The customer service characteristic shown in Giada's book delivery scenario is reliability, which is crucial for achieving customer satisfaction and trust.
Step-by-step explanation:
The characteristic of customer service demonstrated in the scenario where Giada received her books on time after ordering from an online site is reliability. Reliability refers to the ability to provide the promised service dependably and accurately. In Giada’s case, the online site processed her order within the stated processing time of two working days and delivered the books three days from the date of ordering as promised, leading to customer satisfaction. The timely delivery and adherence to the service timeframe is a critical aspect of customer satisfaction and forms the basis for customer trust in a service provider.