A question about 'Past Perfect'
Solution 1:
Think of it in terms of cause and effect. Here the past perfect is expressing the causal relation (by making explicit their relation to each other in time). The cause ususally comes before the effect in time.
More simply, the interrogator quit talking because Barbara showed her 'big winner's badge' (whatever that is). The cause (showing badge/using technique) precedes the effect (going quiet) and thus comes before it in time. The past perfect here is stressing the causality, by putting the first event directly in front of the second, consequential one.