I just had a thought... if you went back and looked at the early chapters, and put the story out of your mind, just looking at the art, how old would you guess Meguru is?
She's consistently drawn noticeably shorter than Kasane or her sister, with a smaller face, too. Looks like a kid, right?
But we were told early on that she was in high school, meaning at least age 15, and
girls have mostly stopped growing by then. In chapter 30 we get exact ages, 17 and 27. Girls by 17 have
really stopped growing, at least vertically; physiologically, Meguru is an adult. If she's shorter than others, it's because she's a short person, not because she's a growing child.
I don't know if it's just unconscious use of this artistic convention:
https://tvtropes.org/pmwiki/pmwiki.php/Main/ShortTeensTallAdults or a deliberate bait and switch. But she's drawn so as to evoke (I'd guess) early middle school, age 12-13, when she's actually young adult, emphasis on adult. We would probably have different gut reactions to the story if she looked taller than either of her 'sisters', which would be 50% likely if we picked heights randomly (given that Kasumi and Hitomi are about the same height as each other.)