I like to think Yoshika was reading her talisman (orders) on her forehead when Marisa asked her the questions there.
Hmm... brain-dead fits the brain part for English, but the subsequent sentence really requires the word "rotten" to be used... 🤔 Actually, it might still work. What if Marisa's reply is something like "Oh, a jiangshi? Ahh... you really are brain-dead."
Reference – Ten Desires, Stage 3