Willow's mother took away her television privileges as punishment for missing her curfew when the punishment could have been much more severe such as being grounded for a week and losing access to her cell phone. Why is Willow's mother using insufficient punishment, according to dissonance theory

Dissonance theory states the cognitive stress that a person hold due to belief in two or more contradictory ideas that goes against each other.

In the above situation, Willows mother seems to believe in punishing to stop a certain behavior from occurring again but she does not give a strong punishment due to her lack of belief in the mere idea of punishing to reinforce a behavior in children.

Therefore she uses punishment which is insufficient,  therefore adhering to both her beliefs.