I mean... she's witnessed that her Fortune-telling has been accurate 100% of the time (except when it came to her future). So it's kinda hard to argue with past results.Why can't she still confess? The whole point of what he told her was that he's trying to move on from his feelings for her which means they are still there. Seems dumb to just be like it's over when she can just blow his mind here by telling him she has liked him this whole time.
Also prior to this current conversation with him, The Crystal ball said that he had someone else he liked that wasn't Shirahoshi but now it's Shirahoshi. This suggests that Otaku isn't trying to move on, he already has after he confessed to Gyaru.
So for her, there really isn't any point in confessing now, especially since this all started cause she pretended to be a fortune-telling gyaru.
Story isn't over though... For all we know, this is all just one long fortune-telling, none of this has actually happened, and they're all still in chapter 1.