No, she's using it wrong. It's supposed to be slap (with the wide side), not chop (thin side).
Slapping give them pain without necessarily killing them. But using it like sword could kill the yukkuri. Unless that's what you want. Seems like Miss didn't read the detail about that.
At first I thought it was a pun on how manuals aren't clear (which way to use a ruler) but the punch line is yukkuri's last words can be interpreted as them being selfish by those who don't know what it signifies.
Book: Afterwards, if the yukkuri can say what it has done wrong the discipline was successful.
Anon: Well then, Reimu Can you try and tell me why I was angry?
(beat)
.....
Huh?
Huh?Can you try and tell me why I was angry?The EndWell then, ReimuAfterwards, if the yukkuri can say what it has done wrong the discipline was successful.Wrong! Please say why I am angry!Want to take... easy mo... Hello reimu-chan?