I'm guessing she either saw him, or her distaste and/or hate for him is so great that just by him seeing her is enough to cause her affection level to fall.
My friend and I figure she's probably going to have an "affection reversal" event where the otaku does something for her and all of her negative affection immediately becomes positive. Or near enough anyways. Like maybe rescuing her from a bad situation with the many guys she seems to like playing around with.
@Nermia01 Yea I was thinking something like that too. Or something cliche like she finds out he's her childhood friend that she has been in love with since she was a kid, and that love is why she rejects everyone who asks her out, as we've seen so far in chapters 2 and 4.
I'll be honest, I don't care how cliche it is, I love childhood friend characters so I'm hoping my theory is correct.
... maybe the author will use for Himekava something similar to gimnick that originally was for Kinjo.
That is, the otaku knows she works there, in this maid cafe, and she asks him not to tell anyone at school. Used as an excuse to have them talking, at least...
I liike Himekawa. If it's done well, I'd love to see a gradual turn around from her affection level than a sudden change of heart. Even if that's unlikely.