The author cheated by not listing an actual 100 reasons list. Could have even made it just 20 or 50 reasons from the beginning then show a giant speech buble, like the blackboard in Komi-san ch 1, to make the scene emotional.
and he on other hand, is more crazy than it's looks.
Both of then are light yandere
reminds me Omoi ga Omoi Omoi-san (where the FP is a not psycho yandere but the MP is also one in the end)
If a yandere demands you to list 100 good things about her, should you obey (to save your life), or should you fail on purpose (to get rid of her)?
I suspect it wouldn't be enough to get rid of her, though.