i know, maximus, i somes call them "flaps-flaps" because the fuck i don't know what are those, but i think that braids kinda became the simplified way to call those.
Prediction: The anon kills the koReimu, but spares the mother Reimu, who has become insane. The mother drags the corpses of her family back to her nest, and believes they are all still alive, all the while babbling on about "happiness".
Regarding the braids thing, it was about a year ago there was some discussion about it. Something about them being literally referred to as piko-piko, that being awkward, and then ending up as braids. And sugar strands/cotton candy is the kind of thing yukkuri hair is (at least that's the most common conclusion). A long time ago again, I think poweryoga posted an interesting link to something (it might have been a Korean delicacy or something like that) that fit quite well.
Also, sideburns has a rather masculine connotation. Doesn't quite fit when you're talking about talking heads based on female characters. At least, that's how it goes around the US. Never hear sideburns when talking about womens' hair.
Looking back on this it kinda irks me that koMarisa seems to garner so little of the mother Reimu's worry. Mother Reimu doesn't seem to display any real favoritism, but for all the freaking out she did over her other two children, koMarisa's torture and slow death gets barely a stammered bit of dismay.