First, a distinction: she thinks that hating someone ought to be about the things they are doing or trying to do, and sensitive to whether there's a chance they'll succeed. She does not think that you can hate people only if you are powerless, just only based on their actual capacities. He asked her if he was supposed to hate her for not caring enough about the paving stones in Hell, and the answer to that, in the framework she thinks her world might use, is no. If he'd asked if he was supposed to hate her for trying to stop him, for being someone who might stop him, then she would have said yes, and given him the symmetry that seems so important to him in believing her that her instincts and principles are not just about hurting him. If he hates her for the fact she would help Broom stop him if she could (if this did not qualify as a betrayal of her word, which she means to keep), then yes, that would be just. Hate based on a true model of her, based on something she really in fact might attempt, and based on what she is trying to do and not whether she cares about things deep in her own heart.
It does seem important to her, that a person in the dungeons of Egorian, hating Abrogail Thrune and wishing her dead, is not the same as Abrogail Thrune hating that person and enjoying herself as she plans their destruction. Carissa does, actually, think that a society of Carissae would embrace the dungeon-person's hatred as an emotion it is not better to erase or suppress, except pragmatically; an emotion that is correct like grief is sometimes correct or like anger is sometimes correct. And she thinks a society of Carissae would judge Abrogail Thrune, for hating the prisoner back, as it would be a hatred out of proportion to the prisoner's actual ability to cause harm.
With that said, there is something to that diagnosis of her, that she is quick to believe herself powerless, that in Cheliax an apparent opportunity to hurt someone powerful would be a test, that they tried very hard to make it the case that apparent power was still powerlessness, that seeing hope was no reason to believe there was hope.
She .....isn't actually concerned at all about a reward for thinking yourself powerless. Being powerless is worse than most kinds of torture. The half-minute in the hallway while Keltham threatened to statue her is more memorable and more vivid and more terrifying and awful than any punishment she's ever undergone save the other time someone threatened to statue her. There's no way any person with a functioning brain would like being powerless.
But a person can be trained to have a very strong assumption that they are powerless even if they see what appears to be an opportunity to change something. And it is actually still difficult to imagine, to Carissa that Keltham would have reasonably believed himself in danger from her in his own demiplane.
(He didn't have security trailing them? He didn't have items with Spell Resistance she had no hope of defeating, and contingent spells set to whisk him to safety if anything happened? He hadn't had someone with Spell Gauge confirm she had no remaining spells prepared and not expended???)