Answer: Deindividuation
Explanation:Deindividuation is the loss of an individual's self awareness, characteristics and real personality when found or involved in a group which can lead to a disinhibited behavior.
A person can deindividuates within a non-violent group or a violent group of which the later is a major source of concern. People tend to deindividuates in a crowd because
1) In a group, a certain type of behaviour can be triggered which members of the group will immediately assume
2.Individual actions may be considered anonymous
From the question, Amy's engagement in a destructive action which went unnoticed during a riot which deviated from her generally applauded behaviour explains how people tend to deindividuates when in crowds or groups.