@Udooky
Thanks, I was about to go read the raw to see that line, since it's probably the most important line so far in the manga.
Miko obviously understands that others can't see it so the choice of words in that particular moment was horribly crucial.
She could indeed more directly talk to the ghost, and then once sensei gets better use that to make him believe she healed him.
But since that's not really in character, she doesn't want him to believe there are things she can see, and that she low-key killed the thing that was weighing him down.
All that to say, thanks for the original line, as well as your take on it.