How does Nikki stop getting bullied by Mackenzie?

Nikki stops getting bullied by Mackenzie by building her confidence and standing up for herself. She seeks support from friends and adults, which helps her feel empowered and less isolated. Additionally, by focusing on her own interests and strengths, she learns to ignore Mackenzie’s taunts, diminishing their impact. Ultimately, Nikki's resilience and self-assertion lead to a decrease in the bullying behavior.