Truth to be told, Sirius Black was never one to be overly attentive of others around him unless the situation actually demanded it. These rare moments were usually reserved for his friends, mainly the infamous marauders, and only them.
Call him ignorant, but he didn't like to bother with the troubles of too many people. He found his own life to be troubling enough already.
Though he may have been quite a womanizer in his youth, none of the girls seemed to wield any power over him, like Lily did over James (not that Sirius envied James, he was rather put off by the numerous and utterly embarrassing attempts of the latter to court said redhead).
Sirius did not yearn to be this obsessively in love, he was content with his rather unattached relationships. He also didn't believe any girl possessed enough beauty, charm and wit to attract him this much.
All in all, he was a hopeless case of a guy with a happy-go-lucky attitude.
Phia was the exact opposite of what the majority expected from a girl. She wasn't exactly feminine nor did she like socializing; she hated to flirt, she was clumsy, put no effort into dressing up and didn't bother too much with makeup unless she had to cover up her dark circles from reading all the way through the night. She rarely spoke, and the few times she did, it was either completely incomprehensible for her fellow classmates or sarcastic (which fewest understood, as well). She had hence almost completely rejoiced into reading her books and conversing with the few individuals that actually possessed the talent to keep up with her track of thoughts. Phia didn't regret not making more friends at Hogwarts, her family came before all kinds of acquaintances anyways. On top of that she was mostly regarded as a weirdo, since her lack of social skills had resulted in her being a bit detached when put into a large crowd of people.
It wasn't like she couldn't be kind or sweet, as a matter of fact, if given the chance she could be as sweet as a cupcake. But her reputation as a misfit and weirdo allowed no opportunities to show this side of her.
That being said one should find it likely that Phia also wasn't the kind of person who would pay a lot of attention to her fellow classmates or her surroundings in general. It wasn't out of the usual for her to bump into someone or something, simply because she was too busy reading or day-dreaming…
