Double-checking my own reading of the part in Chapter 39 where Himawari-san says, “Matsuri is a bit like [the old] Himawari-san in some ways.”
She’s clearly delusional that her brother is attracted to Matsuri the way he was to the original Miss Sunflower.
She’s also mistaken that anyone else who knew that other Miss Sunflower (i.e., her brother, Ayame, the old customers) would perceive any fundamental similarity between the two.
But her brother spells out how Himawari-san might perceive a resemblance—the way the two of them can sit comfortably together supporting each other without saying anything.
And, by extension, the connection is that our Himawari-san loves Matsuri (whether that affection has a real romantic component or not remains to be seen) as she loved the other Miss Sunflower.
Asides:
Himawari-san in regular clothes is really cute, mostly as a change of pace from her regular look.
Fuuko-chan is really cute, no matter what.