These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Alternate Character Interpretation: Is Miharu a mature and normal girl stretched to the limit by her best friend, or a Bitch in Sheep's Clothing who treats her only friend as an annoyance at best? note Yamada tries to be an Alpha Bitch, but it could be argued that Miharu is the one in their friendship who actually acts a bit like one. Yamada never says anything bad about Miharu's boyfriend, while Miharu strongly implies that Kosuda is plain and outright says that he isn't very smart (though it's part of a deduction to figure out whether he knows what Mayu thinks). Yamada may call Miharu embarrassing names like "F cup," but she never wants to stop being friends with her; Miharu's internal dialogue suggests that she's often tired of being friends with Yamada. Yamada isn't embarrassed to introduce Kosuda to Miharu, even after Miharu bounces her breasts in his face to get Kosuda to go on a double date, but Miharu doesn't want her boyfriend to know that she has "slutbox" friends like the virgin Yamada and immediately gets jealous when Yamada talks to her boyfriend. When explaining why Yamada shouldn't write off Mayu as a nerd who poses no threat in appealing to Kosuda, well-endowed Miharu openly talks about how Yamada's breasts (which are shapely and drive Kosuda crazy) aren't as good as Mayu's big ones. When Mayu says she's worried that Kosuda doesn't like her, Yamada is the one who immediately tries to reassure her while Miharu rolls her eyes at encouraging a rival. While Miharu does a good job of putting up with Yamada's efforts to prove her superiority to be "school queen" and not getting openly jealous or disdainful of Yamada's efforts to be the center of attention, she's not very supportive or encouraging when Yamada enters a beauty contest and doesn't do much to congratulate her when she wins. Miharu is demeaning, disdainful, and semi-hostilely sarcastic toward Yamada way more often than the reverse.
Family-Unfriendly Aesop: Not in the sense that it encourages bad behavior (indeed, it's an important lesson to learn and almost unquestionably a good one), but in that it's one rarely taught to young children: ultimately, most members of the opposite gender feel just as awkward about their sexuality (and have just as much sexual desire) as you do, and talking about it honestly and openly is the best way to resolves those problematic situations.
Like many other shoujo and hentai tropes, this one gets toyed with a lot:
At one point, Yamada needs to talk privately to Takeshita about an embarrassing subject, and locks both of them inside a bathroom stall for that. Two girls standing outside wonder if they are lesbians.
In another case, Yamada plans to sneak up on Kosuda inside a dark room and steal his (and her) First Kiss, but accidentally almost ends up kissing Takeshita. She freaks out, saying that if she stopped a moment later she would have to start referring to Takeshita as "Onee-sama".
In yet another case, when Kanejou challenges her to a contest to determine who deserves to be "queen of the school", Yamada fantasizes about what form such a contest might take. Being herself, she immediately imagines herself on top of Kanejou in an extremely cheesyyuri scene (at which point she freaks out again).
More seriously, in the anime at least, Katase has some very suspicious statements ("screw boys..."), especially when Misato is concerned, that could imply that there might be something going on between them. A very one sided something, that is, since Misato's life just about revolves around looking for a boyfriend.