Answer:
Zelda is using a defense mechanism known as displacement.
Step-by-step explanation:
One tends to use defense mechanisms in order to reach a psychic well-being and to cope with certain feelings, emotions or situations.
Displacement refers to taking emotions or impulses towards a specific object and redirecting them to a less threatening object, in order to discharge them in a "safer" way.
Zelda has the urge to set fire to Brenda's car but this specific action could lead to certain issues and could even get her in legal troubles, for example. She takes this impulse and throws pictures of Brenda in a fire instead, thus avoiding further conflicts.