That little pout Himawari-san gives because of her brother's date comment at the end there is really cute. Almost like she's jealous he gets to go on a date with Matsuri instead of her. Because she likes her.
It's not even just that. She spends most of her time in the chapter rather jealous/possessive. Sure, she may have some excuse with her objection to her brother using Matsuri as a model for his book, but that does not quite explain getting in the way of Matsuri taking his photo.