Most of us have measured ourselves against the people around us, and "pretty girl" is about what that comparison does to a person. The speaker begins sure of her looks, loses some of that certainty when she sees other girls, and then finds a new standard. Beauty, she decides, isn't something you wear. It's something that comes out of your mouth. By the end she has turned the usual hierarchy upside down: the girls who look perfect are "not pretty at all," and she, who is never described, is.
The first stanza is built as a loop. "I always thought of myself as a pretty girl / until i saw other girls, / then i thought of myself as a pretty girl / until..." The same phrase comes back with a new "until" attached each time, so her confidence keeps getting interrupted and rebuilt. The syntax is slightly tangled, and the poem never says outright whether the comparison shook her or not. That fits the subject, since self-image rarely moves in a straight line. The pivot comes in the long fourth line, which runs on well past its neighbours as the other girls "opened their mouths and said things that weren't pretty at all." The line's length mimics the talking it describes.
What follows is a short, steep descent: "their words were ugly / their hearts were ugly / their soul was ruined by the cursed words they spoke." The structure is a triplet that moves inward, from speech to heart to soul, with each step more serious than the last. "Cursed" is the strongest word in the poem. It borrows from fairy tale and religion, as if cruel talk were a spell that damages the person who casts it. There is also a small grammatical wobble, "their soul" in the singular, which makes the girls sound like one collective figure rather than individuals. The speaker is already turning them into a type.
The second stanza turns that type into a list. "With pretty faces / with their pretty makeup on / and their pretty hair / and pretty clothes." The repeated "with" and "and" pile up surface details, and the constant "pretty" starts to sound hollow, the way any word does when it's said too many times. Then comes the quiet hinge of the poem: "i listened / i listened to their pretty girl words." The repeated "i listened" is the speaker's own act, patient and a little sarcastic. "Pretty girl words" welds the label onto the speech, so that "pretty" now sounds like a brand name or a costume, not a compliment.
The ending is the most carefully timed part. "Until i realized / they aren't pretty at all" echoes the earlier "weren't pretty at all," but the tense has shifted from past to present. An event has become a settled verdict. Then, after a stanza break, comes the shortest line in the poem: "but i am." The "but" does the turning, and the blank space before it is a pause for breath. Notice, too, that the speaker never describes her own face, hair or clothes. Her prettiness is simply declared, and the poem gives the other girls all the imagery. The lowercase "i" used throughout keeps the voice informal, almost like a diary entry, which makes that final claim sound stubborn rather than boastful.
The poem is easy to admire for its message, and it is also worth questioning. Its central idea is a familiar and worthwhile one: how people speak and treat others matters more than how they look. The poem makes that point with real economy, using one repeated word and no rhyme at all, so that nothing distracts from the shift in meaning. But the speaker's judgement is sweeping. She hears some girls say ugly things and condemns "those pretty girls" as a group, and her last line could mean "I am pretty inside" or simply "I am still the pretty one." The poem never settles which. Perhaps that ambiguity is its most interesting feature, because it shows how hard it is to escape ranking people even when you're trying to argue against it. Whether the poem knows this or not, it gives a reader plenty to discuss.