I like that we get to see these previously off-screen moments. It's also great to know Shiho isn't just a side character with no impact at all on Sei and Tsukasa's growing almost-relationship, she's a believable friend helping Sei behind the scenes and is directly responsible for Tsukasa getting to enjoy the view of Sei's bellybutton on the day of the date.
The line "Sei-chan's style is great" on page 3 actually refers to Sei's figure/bodyline and not her fashion if the original Japanese used was スタイル "style", which happens to be a loanword in Japanese with a different meaning. So it should be "Sei-chan's got a great figure" which ties up neatly into the next dialog with how Shiho is elaborating further on what she meant by "great figure", rather than seemingly going on a tangent from Sei's fashion to her body attributes.