And that's exactly why she was kept until the very end. She's getting the job done, so the emperor kept her even if he disliked her. So now the emperor has an 'ally' (concubine) that is as wicked as he is, and he has Robelia, who's doing all the empress work. The OG/Book Robelia would probably never betray the emperor because that's how she was written. That's what frustrated the 'new' Robelia. OG Robelia spent her entire life doing things for the sake of others.