The conflict is the central problem of the story and is what the story is about. The theme is the message of the story, so it can't be the answer. The protagonist isn't a problem, the protagonist is the main character.
I believe it would be to inform, the particular excerpt isn't really informing about anything, and its not persuading the reader to do anything, simply attempting to entertain the reader with a story.
The story is trying to convey the message that being attracted to someone, or being infatuated, is not the same as true love. The teenage girl feels excited and happy to have someone care for her, however, the boy is not serious about her. He wanted to "pick her up" but had no intention of ever turning this passing flirtation into a serious relationship. The story also suggests that not being able to distinguish between these two different types of attention can cause a lot of heartache and confusion.
The words the author choses are those that resemble the speech of a teenager. This allows us to sympathize with the girl by making it easier to imagine the types of thoughts she is having. The author also uses some rhetorical devices such as anaphoras (the repetition of words at the beginning of neighbouring clauses), similes and metaphors. These use of words contributes to the theme of confusion and pain that comes from confusing superficial flirting with serious attraction.
