I was also wondering why she stopped appearing. So I checked around.
The event tab in game says the event is ongoing and that it doesn't end for another week. The front page of nutaku is similar, as it still has the event graphic.
However, on the games page, if you scroll down below the game window itself, the event says in smaller print that it ended on Oct 31st.
So on the one hand, it was an innocent oversight by the game devs. On the other hand, they did it on purpose to mislead people into thinking they had more time. Who's to say?