The speaker starts out confident, believing she is a pretty girl. That belief wobbles when she meets other girls, then returns, then gets tested again when those girls speak and their words turn out to be cruel. The poem keeps repeating "pretty" until the word starts to feel hollow, which is clearly the point: the speaker moves from judging people by looks to judging them by what they say and how they treat others.
She describes the makeup, hair and clothes carefully, almost as a list of surface things, and then sets them against "ugly" words, hearts and souls. Listening is what changes her mind. By the end, she decides the other girls "aren't pretty at all," and then adds the quiet, firm line, "but i am."
The mood is blunt and a little defiant. There is hurt underneath, but the ending feels like reclaiming her self-worth, even if it also shows a bit of pride and judgment of her own.