I think the joke at the end of this chapter can be made to work in English. Some possibliities:
"Himawari-san, 's a lot prettier than before."
The "'s" being an undervoiced "it's" that's makes "Himawari-san, it is" misheard as "Himawari-san is." This mimics the dropping of pronouns in Japanese in a way that sounds more natural in English.
Or, use punctuation to make the intent clearer:
"Himawari-san--'s a lot prettier than before."
The dashes represent an introductory clause or an omission.
Or, taking some more liberty with the text:
"Himawari is a lot prettier than before."
This creates a scandalous ambiguity between referring to the bookstore and being very forward by complimenting her while not using an honorific.