Answer : 1. "Reserved"
Explanation :

The word "reserved" is the most suitable choice to fill in the blank because it indicates a lack of outward expression or enthusiasm. If someone becomes reserved in a conversation about a certain topic, it means they become more restrained, quiet, or less willing to openly share their thoughts or feelings. In the given context, it suggests that the person's demeanor changed to a more restrained or withdrawn state when discussing her father.