In the end, Marisa disintegrated and died. The inside of her body must have been torn to shreds by the yukabi. When she was revived from the anti-yukkuritis condition, she was unable to go crazy due to the "happy'' component of her mother, Reimu, that flowed into her.
The next morning after the moldy growth, Marisa's condition became more serious. Fortunately, today is a day off, so I think I'll be able to observe until the end.
When I went to check on Marisa before going to bed, I found that she had fallen from the stem and was sleeping happily. I guess she was draining bad memories and having good dreams.