Revenge is pointless. She's garbage, not worth it.
Oh, but she's just a child!
So what? Where do you think garbage adults come from? She's not going to magically turn into a decent person when she turns 18. Will she change? Maybe. But that doesn't mean Nack has any obligation to associate himself with her.
Best thing Nack can do is finish the fight, flip everyone the bird, and go find people that appreciate having him around. Toxic people aren't worth the time or trouble to deal with.