I don't think Kanae can really picture herself in a romantic context at all so Haruka really first needs to get her receiver tuned to the same station, so to speak. I get the impression the way the former keeps awkwardly shrugging off some fairly obvious signals is her way of coping with an concept she can't really process (on top of the usual uncertainties of interpretation ofc).
After all, outside her StuCo role she tends to be pretty quiet and withdrawn even with friends - I suspect the idea she might actually be the focus of someone's attention like that confuses her greatly.
On another note Michiru definitely got the hint and hastily committed a third wheel, exit stage left. :P
As far ask Mask and Kaoru go whatever else Bou-chan might feel in regards to her admirer I think the key phrase here was "something only I possess" in the context of her creative frustration. Fresh novel stimulus outside what you're used to is one of the better ways to get those gears turning again and Kaoru's certainly by far the furthest from her usual associates in terms of people she knows. Bonus points for the whole "school Casanova is head over heels for you whether you want it or not" being a storyboard basis all by itself I suppose...
Speaking of, isn't this Kaoru's first appearance in over a volume or so? The unnamed girl in the library may have shaken her out of her funk but she's apparently treating Mask's fuck-off verdict with due seriousness and keeping her distance. Probably been passing the time flirting with random pretty girls in the meantime.