Who visits Q near midnight one night and what does she want?

Margo visits Q near midnight, climbing over from her room next door to Q's house into his room. Margo wants Q to help her run a number of errands with his parents' car. Quentin eventually agrees to take her to Publix and then Walmart. Margo needs to buy some items and has hundreds of dollars saved from her Bat Mitzvah. She tells Q that he is going to have the best night of his life.