^
But yea, the fact that Menma can physically interact with objects kinda points her towards being a ghost rather than a hallucination. We have no means of proving that ghosts (if they exist) can interact with physical objects in real life...but seriously, she ate some food. I don't think a hallucination can eat food lol. Also, I don't think hallucinations can wander away from the person experiencing said hallucinations lol.