Kavinsky was never fine. He wouldn't know fine if it punched him in the face. He was, however, successfully distracting the ghost, so that had to count for something.

He was also vaguely aware of what Mary was doing, but didn't look at her just in case the ghost took notice. So when the pitcher connected with the mirror and the glass shattered, he flinched. The ghost whipped around and screamed in rage- before flickering out of existence. Kavinsky didn't think it was gone for good, as in, sent back to the afterlife, but it was gone for now and that was almost as good.

He'd stopped laughing at least, as he looked curiously between the mirror and Mary. "Right- he said something about mirrors, didn't he? Good thinking."