I don't think she knows much more. Didn't the librarian say everyone forgets about the ghost and whatever after the year is over? Apparently in her year it stopped after the summer, for whatever reason, and I think she genuinely doesn't know any more about it. She was obviously hiding something from MC, though, before this episode. Why? Doesn't the curse affect only the people connected to the class? I mean, everyone else can interact with the ignored just fine - including the old teacher. The only reason MC got into this mess is because no one - including Reiko and Mei - told him about the rules. But now the aunt is talking to him, which means she isn't currently involved. Messed up.
I think the key is what happened in Reiko's year, since that is one of the few times the curse was stopped. I have a theory (my spoilers didn't cover this): Since the whole trouble is that people aren't killed when they die, and they apparently do at the end of the year, which ends the curse for those kids and everyone forgets, etc., then perhaps what happens is that the curse isn't connected to the school year, but to the stiff - if they become more deceased, the curse is over. So, somehow, fifteen years ago the dead guy got killed, and the curse was over for the year.
I'm also guessing that the curse can't be ended permanently for some reason, because this is Japanese horror and there are no permanent solutions (other than everyone dying, maybe).
"You perceive wrongly. I feel unimaginable happiness wasting time talking with women. I'm that type of human." -Sousuke
"I especially like cleaning the toilets...
At times the words "latrine orderly" flash through my mind, and I feel somehow dutiful.
Once on a nature channel I saw great icebergs of Antarctica. They gleamed and glinted, cold, forbidding, pure, and white.That's what I strive for with the toilets."
-Excel