Oooh, a space time cat. Yeah those are real handy in a pinch, you know? I was about to say we were due for meeting one, seeing as Itsuki totally pussed out on being helpful with a nonsensical excuse.
I mean, really I can't really think of a better reason for her to be like this than she doesn't like herself because of something she did, misunderstanding or not, and prefers to think about other people since thinking about herself is too depressing. Would explain why she's always so cheerful. She's hiding some demons in that exhausting display of enthusiasm. Our boy is probably going to feel terrible when he realizes he doesn't really know her at all.