Because Rose was a worse daughter. Lilia has no sympathy and vaguely wishes they weren't talking about it. 

"It's not an easy thing, to be a tool of the will of another and then turn out to be only all right at it. I am sure I'd have more complaints if I hadn't been good enough. But that'd have been - my weakness, not yours -"

"If, someday, you wish to be more than just a tool of my will...A friend and companion, say," Or your own person living your own life never having anything to do with Catherine again - but if she said that Lilia would take it as rejection - "that would make me very happy."

Lilia is pretty sure that this disconnect here would not be solved by explaining to her mother that it would be an important failure to someday develop a desire to be something else.

There is a disconnect, though. Unless -

"...would that really make you happy or are you feeding me lines I can truthfully share with Alex?"

"...Please don't tell Alex I said that. It would really make me happy."

That's just discomfiting. "Of course," says Lilia automatically.

"When you're ready. I'm patient and in no hurry…How is it going so far, befriending Alex? Does he let you call him that, yet?"

"I haven't tried. Maybe next loyalty check…I really look forward to them."

"Oh I'd advise against bringing it up. Maybe try 'Alexeara'. I think if you just call him Alex you'll remind him of me and that's counterproductive. What is it about the loyalty checks that you enjoy? I imagine in your place it would feel - vulnerable. Like standing in an antimagic field."

"It's terrifying. But, you know, I think I'm missing a sense of thrill and danger in my life, now that the youth have it easy and the worst the paladins will do is politely let me know we can't keep working together. And he - relaxes around me. It's a bit like the difference between you when you have guests over and when you've Dominated them. Except in a paladin way."

"There aren't very many people who I'd sit still in an antimagic field for because it helps them relax in my presence."

Well, see, Lilia's never had anyone be nice to her before. Saying that will really ruin the mood of this tea.

She shrugs. "If I call him Alex it'll remind him of you? When have you two ever met face to face, the moment he murdered you?"

"Oh, then, a couple times before. When I was provoking him. His friends call him Alex, see, for everyone else it's 'Alexeara' or 'Ser Cansellarion', and of course I'd dominated a few of them and was taunting him with the familiarity. It really got under his skin very effectively, for such a small thing. And once or twice in negotiations during the war, once he knew it was me. Most people, he'd just correct, but from you I expect he'd find it reminiscent."

"Yes. I am glad you warned me. …if I succeed at seducing him, and it's going to be very challenging, would you mind, on one occasion, being in my living room as yourself the next morning, with breakfast?"

What.

"Of all the favors you could ask of me. Do you mean shapeshifted into Myrabelle or just as I am now?"

"No, no, as Myrabelle. …I care about him quite a lot but I can't not poke that, now that I know more about it."

"I wish you the best of luck, pursuing him. Ask me again when you've caught him, if you still want me to do that, and I will."

“I expect to have time next week,” Alexeara informs Lilia, “If you still think it would be valuable for me to watch you working.”

She’s worried that letting him watch her will be either counterproductive for the project of seducing him or counterproductive for the project of figuring out why she thinks interrogation is probably Evil and actual Good people don’t seem to think so. (Counterproductive for the first if she doesn’t play nice, counterproductive for the second if she does). However, Lawful Good Lilia would absolutely do it. Lawful Good Lilia cares about philosophical disagreement for its own sake, and also doesn’t want to talk to Aspexia until she’s settled this. “I’d appreciate it.”

Seducing Alex is not strategically important in any way and is mostly a bonus task she set herself so she wouldn’t get bored; it should not be the thing that wins out when priorities are in conflict. She notices a vague nervousness anyway that he’ll be disgusted with her. Well, if he is, it’s because he was lying to himself all along about who she is and that’s pretty contemptible of him.

Lilia’s department has other people who do the things that the Reclamation likes to try first, before you resort to magic; negotiation where one party holds all the cards, trying to build rapport with people, etcetera etcetera. Lilia only bothers herself there if an asset is extraordinarily useful. not because she’s no good at it - she’s very good at it - but because it’s slow and she’s very busy. She does all the Dominates herself, because as a technique it’s not very forgiving of error and other people have less finesse with it. Then someone else gives everyone the chance to object to their treatment, say anything they want about the case under truth spell, etcetera, but that all mostly feels like window dressing on the part where they learn anything they need to know. (She’s prohibited from asking them about most things she doesn’t need to know, but she never really bothered with that anyway. She’s busy, and while it’s fun to learn someone’s deep emotional vulnerabilities and so on it’s rarely a good use of time.)

What is a good use of time is to command useful appropriately thorough nonmisleading answers and then get a timeline and a confession to all relevant crimes and a network of relationships and accusations against those people and rumors on topics of interest to her. She reads their minds while they speak, asks about anything important they seem to be trying to hide, makes them search their own memories for more people to betray to her. She has them speak quickly, often quickly enough no one can understand them but her; it saves time. She permits them to fidget, this being a Reclamation rule, though it often results in subjects thrashing around like a beached fish which strikes her as embarrassing enough she’d personally prefer to be forced to hold still. Mostly, though, she doesn’t contemplate at all what they’d prefer. She finds interrogations much more akin to having a report read to her than to interacting with a person. The person stopped being a factor in the situation a long time ago; what remains is everything that they knew.  

She has decided not to indulge the impulse to avoid scaring Alex off, but she does indulge the impulse to impress him, mostly by using rather more of the good interrogation spells she knows (the ones that make someone permanently more vulnerable to your divinations and let you pull memories directly out of their mind) than she’d typically bother with for what’s evidently not a very good plot by the remaining Church of Asmodeus. 

She still doesn't have an articulation of why this seems Evil, or indeed of what Evil is, but she is (despite the many reasons not to expect this) vaguely expecting him to be upset once he's actually witnessed it, even though she's followed all the rules.

"...What happened there?" he asks between interrogations, about a prisoner who was thrashing violently in her chair. "Was she suffering?"

"....presumably? Wouldn't you be, if captured by your enemies and obliged to betray all your secrets to them?"

"Yes. I mean - was there anything else."

"No."

Well, apart from that Cansellarion does not actually see anything objectionable here, and suspects that Lilia’s difficulty seeing the difference between this and torturing information out of people is a product of Lilia’s life experience deadening her moral intuitions. Or she gets a lot of violently thrashing Asmodeans, in which case perhaps he too ought to reconsider. "This is a very efficient operation. How often do you get people reacting like that, out of how many people?"

"Moving around a lot? Less than a quarter. It's more common with non-Chelish people." Probably because those are likelier to imagine she'll care. "I'd make them sit still like civilized people but that's against the guidelines I was given, if they're not actually impeding the questioning."

That is a mildly troubling way to phrase it.

"Please continue to not do that. I would like to speak to that woman, not under a dominate."