I need to get rid of my chewing gum. I might put it in this uppity girl's hair.
That's an awful thing to do. Why would you put gum in her hair?
So she wouldn't be so full of herself.
You shouldn't want to do things that are not right. Sticking gum in a person's hair is mean and unkind. People will not like you if you do these things.
If they knew it was me they would like it.
Sounds like you might be a bit of a bully. Doing mean bully type things to other people doesn't make bystanders like you or what you're doing. It only makes them afraid of becoming your next victim.