The cycle of attraction--following everything is 'real--is always:
Curiosity>discovery>attraction>pursue>relationship (assuming everything went well, abridged version)
Following that, it's a lot simpler to divide some of the scenes and put them in each respective category, I'll agree on the notion that Hanako may have attraction on Hisao starting on their 'walk' together.
Since her story takes about 6 weeks total, yeah she does get attraction relatively quick--not sure if it's a good thing or not, but eh, wtv.
And is it just me, but is Lilly being a bit of an irritation in her route? She does play the matchmaker, but the fact that she's looking 'down' on Hanako is not far from true, whether you want to argue it as being 'motherly' or not. She has been doing it for a long time before Hisao enters the scene which is...quite desturbing.
So wouldn't it be safe to argue that Lilly is also Hanako's 'pacifier', so to say? She does have the potential to make friends--it's just how Lilly treats her that 'keeps' her from doing so.
Now on to Shizune.
I'll argue that just because Misha likes her, doesn't mean she has the obligation to like her back. Her disability and overbearing personality--funny enough--plays along the audience's incapability of fully grasping her character (just as she's having a greater difficulty to communicate her thoughts compare to other girls) and most of what she's trying to convey is lost with Misha's translation. This does not make her treat Misha as a 'tool' (for if she did, as what most people believed, she wouldn't go into the trouble of trying to mend their relationship--even risking her own relationship with Hisao in the process--when she could just rely on Hisao as her new translator and disregard Misha entirely). To me, Shizune has a very playful and competitive personality and often tries to bring the best out of others (though not often is it welcomed by most) so she could talk with someone of 'equal' standing.
She knows Hanako is good at chess, thus she challenges her.
She knows Hisao is capable of standing as her equal, thus she tries to coax him into the student council.
And I dare say she wants to make ammends with Lilly, but as long as the other party refuses to do so she can't make a move without causing another argument (pair that with Shizune's overbearing personality and you'll have instant-classic misunderstanding)
Also...
Notice that Hisao has a bit of everything of all the girls? And that each girl brings out the best in one of them or most/all of them? Further, he has that 'mysterious transfer student'-vibe when he enters the classroom, a big plus since you tend to gain more attention than your average male.
On to OCs...
OCs are Original Character, so your interpretation of Hanako is just that--interpretation. OCs are original characters that you created and originally does not exist in the original storyline. Which makes NTR Hanako or Yandere Shizune isn't an OC but more of interpretation and a bit of OOC (out-of-character) moment, usually written...just because.
