I was just watching the scene where she has Queen Sareth's fertility examined and she tells her that she was the one to kill Sareth's family.
First things first, Laura Birn has an incredible ability to produce a number of Mona Lisa-like faces where you can read 10 possible emotions into her at once. She has absolutely DEVOURED this role and plays Demerzel extraordinarily well. I hope one day she gets an award for the role.
Regarding the scene, it's absolutely fascinating. Obviously, to examine a potential empress' fertility, the best medical environment is not one with dozens of people in the room. And in the year 50000, well, surely they could have made the examination painless. But the examination was both painful and humiliating for Sareth. Which works really well for Demerzel's character on a number of levels.
Obviously, the simplest way to read to scene, on a rewatch at least, is that Demerzel is bullying Sareth and treating her as poorly as possible so that she'll get emotional and careless. Nudging Sareth, already somewhat of a hothead, to feel anger and strong negative emotions. Which will make her more likely to make mistakes, politically speaking. Especially by telling her about having killed her family, she's psychologically breaking this woman, lowering the union's chances as much as possible. I haven't said it yet, but obviously all of this is so that the marriage will fall through and the Cleonic dynasty continues.
However, Demerzel is more than her programming, so it stands to reason that Sareth having learned about her robotic nature, and having talked about it in public, would have pissed her off too. For anyone, to have some brat loudly spilling your secrets would piss you off. Also, she's probably mad that Sareth found out about this without her (Demerzel's) knowledge. She's irritated that this girl is as capable as she is. And if robotic psychology is anything like a human's, she's primed to dislike Sareth on the grounds that she represents everything she's programmed to hate. And if you're gonna have someone killed, it serves a certain purpose to literally dislike her.
And I just love the number of ways you can approach all of Demerzel's scenes. Knowing her nature changes the viewing experience of the first two seasons SO MUCH!! You can pick apart any scene, any look, any dialogue, and find a way to interpret what she's thinking and why she's saying what she says.
Take the Brother Day of this age. Before he first attempts to sleep with Sareth, his scene with Demerzel is HILARIOUS. She's cheering him on like he's a dog lollll.
I also find SO FASCINATING the relationship between Demerzel and each Cleon. For example, on season 1, I fully believe she deeply hated Cleon 13. She would NEVER forgive him for ordering her to kill Zephyr Halima. That broke something in her. She loves every Cleon, not just because she is forced to by programming, but because she's their mother. She's raised every one. But him commanding her to needlessly murder a woman she considered holy.... Shit got personal after that. I truly do believe Cleon 13 is her least favorite, after Cleon 1. And I think part of the reason she killed Cleon 14 in the exact moment she did was to hurt Day!!! She was never gonna let him live, he had been altered to stray from Cleon 1's design. But she killed him right after Day said he wanted him to live. I think part of it was to hurt Day for what he'd made her do.
Regarding Cleon 17, Season 2's Day, I don't think she hates him in the same way. I think she feels contempt for him, and she did call him "A sperm led by its waving flagellum, mistaking its random motion for complexity," which might just be the best read in science fiction lollllll. But she clearly felt some kind of pity for him, she considered she had failed in raising him right. She hated the kind of man he'd become, but she didn't consider his poor character to be his fault. She treated him like one would a mentally ill pet, or something like that. Whereas Cleon 13, a man capable of some degree of empathy and kindness, having ordered her to kill a woman she admired, just as payback for her having knelt when Halima spoke heresy against the Cleons.... She hated him more, exactly because he was more than a "waving flagellum".
Anywaysssss, rant over lol. I just love Demerzel so much, I could talk about her all day