It's what came to mind first to me too, but it's important to realize that you can't easily go by a translation's exact wordings as foreshadowing.The "You'll never understand" is foreshadowing Eito becoming a girl, right? Like, I know that I'm a bit biased here, but surely that's how everyone else is reading that, right?
Uesugi: I am the one who says gexGetting your fellow guy friend to call you cute.. to what end, Uesugi?
Or it's a fake-out and she is blushing because she has a fetish for guys turning into girls and suffering with menstruationOoooh. Glasses girl wants some of that Eito action, eh? 🤔