I'd love to know how real wota feel about the director's portrayal and Sayu's reactions. Regardless of whether it was all a practical joke, the stereotype is what it is and Sayu is clearly playing both sides of it.
SayuReina was awesome, but I really wish Reina would have tsukkomi'd Sayumi a bit. That goes much better with her character and they'd have been even more hilarious. I kinda love that Hamachan went all "Whateveeeer" when soemone asked him to go tsukkomi on them though.