-Florean Fortescue, who is in Ravenclaw with Sybill. He is sweet and adorable and willing to offer up free home-made ice cream at any and all opportunities. Also, he can actually see the future on a regular basis, though he is much less prone to admitting to it, so Sybill may intimidate/make him nervous a little.
-Barty Crouch, Jr., who secretly dislikes almost everyone, but he's probably going to ACT polite to her.
-Ralph Macmillan, who is probably a little bit skeptical of all the future-seeing business and may not be very good about trying to be polite about his doubts on that front. But he isn't mean, by any means. Just doubtful and occasionally very bad at being politically correct. Also, he is very dedicated to his duties as a prefect, so as long as she doesn't go around breaking rules willy nilly, he approves of her.
-Professor Benedict Ogden, who teaches Arithmancy and tends to think most students are complete idiots and treats them accordingly. If Sybill's in his class, he will expect her to do the work or he will cheerfully flunk her.