i think they're having fun with Dedra's enigmatic reaction to significant moments - i don't know where she lands on 3 of her scenes:
Does she hate or is intrigued by Syril's stalking?
Did she appreciate her assistant piping up in the meeting about Andor shaving or did she find it concerning?
Did she appreciate her assistant taking initiative about 'interviewing' the Rebel pilot or did she find it concerning?
All ruthless people believe that their underlings are also ruthless, therefore a danger. Look at the Sith dynamic. Only two, a master and an apprentice. The apprentice kills the master, becomes the new master, takes on an apprentice, and so on.