Everything said after she holds up the picture on her phone makes absolutely no sense to me. Who's supposed to be in the picture other than her? What does she mean by "you" being him? Up until that point it was fine but then it's like Google took over.
I don't have raws to confirm, but here is my contextual understanding:
-Rin (the long haired girl) was, as is usual in Japanese, talking without pronouns.
So essentially Rin said [X] has been appearing on Himari's (the main girl) Instagram, while holding up a picture of Himari, while talking about the person she likes.
-From this, Himari considers for an instant that [X] might be herself, which would basically be an indirect confession.
She quickly realises, recalling Rin's speech from just before about "capturing someone's heart" and "liking someone whose face you have never seen", that [X] is in fact the earrings. This would imply that Rin is in love with Yuu (the MC), so she gets jealous (though she herself denies this) and goes into denial.
-Thus, Himari fakes ignorance of her second conclusion ([X] = earrings) and pretends that she still believes her first conclusion ([X] = Himari), and replies with "Wait, you mean you like me? I thought you hated me?".
Rin quickly shuts this down and says/implies something along the lines of "You know very well that I'm talking about the earrings. It's Yuu who made them, isn't it?".
-Himari is forced out of her denial, and now has to accept that Rin is in love with Yuu, which makes her afraid of losing her relationship with him, as she continues to struggle internally with whether or not guys and girls can "just be friends" (the title and main theme of the manga/LN), now from a new perspective - what if Yuu gets a girlfriend?
Props to the author for writing all of the above implicitly.
This seems like a crucial turn in the story as well so it's a shame that the translation didn't do it more justice.