Naomi is still in shock, a bit -- Headmistress McGonagall has only just left her house and now she and her parents are off to buy school supplies. It's nice to have explanations for the weird hats and the broken video game system and the time with her school sprinklers, but it's not nice to not get a decent answer to why everyone doesn't know about magic. Obviously they should, it helps so many people, the headmistress said so many nice things about how safe magic is and what she could do when she's grown up so her parents won't worry.
She probably needs more information. Books help with that. Asking people helps -- and she's good at asking people for information she needs. Computers are supposed to help with that, but apparently they don't work near magic, and isn't that just terrible. She'll probably have to leave Hogwarts regularly so she can do experiments, or maybe sneak some of her things to school with a sufficiently large trunk, she could maybe get her parents to get one of those for her if she asks for Christmas and her birthday.
Now she's in the bookshop. There sure are a lot of books and she has no idea which ones will be helpful other than the school ones she's supposed to get.