Glorioa is gorgeous! And yes, their history makes perfect sense. Maybe they were well synced, getting him to the throne, and that relationship suffers now, quietly, and they both feel it. He feels bad for it, when he thinks about it, and she can have turned to scheming instead.
He could have promised her a higher post, but now sees it like strange favoritism since he's not the king. I feel like he's inclined to give her anything she asks for, though, so she could use that with her scheming. I can even imagine her offering her a position of queen, and her not taking it because it feels like pity, I dunno, does that work for her, you think?
He might even defend her if she's accused if she ever slips with her scheming. I imagine he might also get defensive with her, since she's a blaring reminder of what he could/should have been, when they're on their own.