@Goronthil Well, most of it's black and white so you can't tell the hair is pink except on the cover and, yeah, like
@icarushector -- it actually never occurred to me that the cover having pink hair meant her hair was actually in a real sense dyed pink, although I guess maybe it does? I'd have expected that to cause serious problems with teachers though. So that leaves "She likes fashionable clothes" (which surely is something that extends to a fair number of high school girls one wouldn't consider gyaru) and "she's a bit lacking in defences when it comes to seeing cleavage etc., especially with her new 'brother'"--which applies to every sister character in a shounen manga, ever.
But she doesn't talk like a gyaru and she doesn't seem to do gyaru makeup or even have a tan or in general do anything culturally gyaru except like fashionable clothes. If this is now considered gyaru, I think Japan must be experiencing a cultural shift to "even more conservative than before".