I'm going to go out on a whim here and say that Shanna is just a very peculiar girl who has some weird ticks while a select few of her servants are either downright evil or that their actions are why the rumors of Shanna being a witch came about
@Thirtyfour I wouldn't be surprised to hear that the author is starting to run out of ideas and is slowly coming to a stop with what he can do with the series. Which would make sense considering the nature of the manga's gag
For some odd reason, I thought that the Prime Minister was going to somehow turn out to be her dad and not her ex-fiance.
@Darkmint13 From what we know about her, she's an airhead so I'm sure that they told her that the two of them were going to get married at one point, but she misheard them...