Maybe their height difference was because Shinah was closer in perspective? Anyway, I never pay attention to such detail, so it doesn't really matter to me.
I noticed the same thing. Funny, but it didn't really bother me
It didn't get to me much at first, but I've read a few of the author's works and they all do the same thing. It's one thing to just have inconsistent heights, but she spends a substantial amount of time telling us how tall X-kun and Y-chan are, but then just disregards it and draws them however she wants anyway. Like...why even bother then lol?
After rereading this (insomnia + super boredom = rereading random manga lol) I realized that this author is somehow REALLY inconsistent with her heights! It was prevalent throughout the entire manga, like every scene with Ida standing next to Naru showed a really small height difference despite him being super tall but I kinda ignored it and convinced myself that maybe she was just really tall too lol.
BUT! This page literally had me rolling on the floor laughing! http://www.mangago.me/read-manga/he_s_dedicated_to_roses/mf/v11/c042/65/
How is Shinah, at 177cm taller than Naru at 191cm? ブハハハ (≧∇≦)人(≧∇≦) ブハハハ
If the author couldn't keep the heights relatively consistent, why bother going out of her way to define them lol?