I really don't recall who came up with the idea of palling up Koishi and Flandre, but it doesn't seem THAT bad of an idea: the impression I'm getting of Flandre is that she's not a psycho but has little sense of self control and no one's really tried to correct that behavior of hers. Koishi's a tough cookie and might get along with Flandre.
Though, honestly, it might be a better idea to wait until AFTER the incident's dealt with before setting up Flandre and Koishi so Reimu can properly make sure no one gets their faces murdered supervise. At least float the idea to Koishi before we continue on.
> "It's not 'falling' if I'm doing it on purpose. Speaking of, how's... uh, that squeaky girl doing?"