The speaker begins by pointing out a girl in different places: reading in a corner, working alone at a table, sitting on the grass with her shadow. Each time, she seems absorbed in what she's doing, but the poem keeps revealing that she is really paying attention to everyone around her. Her book, her paper and her patterns in the dirt look like distractions, but they work more like cover.
The fourth stanza gets quieter and more honest. She is waiting for someone to look past her flaws and stay with her. The last stanza delivers the twist: the girl is the speaker herself, and she knows she was noticed after all. Calling herself "that poor girl" sounds both sad and a little wry.
The mood is lonely and gentle, with a hint of vulnerability. The repeated "See that girl" pulls the reader in, then turns the question back on them: did you really notice?