Syntax refers to the way a sentence is put together. The typical sentence contains a subject and a predicate, and then perhaps, in addition, a direct or indirect object, some prepositions, some adjectives, and so on. Any deviation from the norm is going to draw attention to something in that sentence. For example, a sentence that lacks direct reference to a subject (which would actually not be a complete sentence, then) might draw attention to the predicate instead.
In "Girl," the speaker, presumably the girl's mother or a female authority figure, is issuing a long series of instructions on all manner of subjects that are necessary for this young girl to know. Rather than placing a period after all, or even some, of the independent clauses, the author chooses to string them all together with semicolons, creating one gigantic sentence, full of directions and orders.
Although semicolons are used to separate independent clauses that are strongly related, we typically don't connect more than two or three independent clauses in this way. Therefore, this is an unusual syntax choice that seems to emphasize just how much responsibility this young girl seems to have thrust upon her and how little agency she has to make her own decisions, as every moment of her day seems as though it will be filled with the tasks her mother outlines. Furthermore, the almost complete lack of the girl's own voice seems to imply that her identity and voice will, in fact, be stifled by her life as a girl (which the title seems to imply is the most important part of her identity).