Walking to bouldering and thinking Theo thoughts. I'm just still thinking about that conversation she and Cas had and like. There was so much she could have said that she didn't but like. Okay. So, Theo thinks she's a bad person, right? Even before murdering a whole bunch of innocent folks, she considers her existence to be a selfish one: she takes what she needs and survived. That was her life. When her sister found happiness, she scorned her bc she was scared of what it would mean for her and for them.
On the other hand, she thinks Klath'ra is a very good person. They look out for all their kids and rage against the machine and protect the people they love. Right? Like, she doesn't think poorly of them for the Mephistopheles stuff bc she knows they had no autonomy in that: they took the deal with the devil to help someone they love. In her mind, it's very noble.
She, on the other hand, took a deal with a devil on the selfish desire of having her love back. This is irredeemable bc there's no wider good in that, it only serves to help her. Furthermore, she placed the life of the person she loves (and, to a lesser extent, her own) above the lives of hundreds of people. This is despicable and irredeemable; if she told Klath'ra or Laudine, they'd hate her forever bc it was an evil thing to do. She's confident that Cas and Ronzur hate her bc they've seen her make this selfish choice. On top of this, she's also sacrificed her brother and the only real friend she had as a kid for that same choice.
Like, call me insane but there's a parallel there: they've both done bad things for the sake of each other. Klath'ra is excused bc it was for the person they love, Theo is condemned further for the same reason.
I mean, there's also the element that Klath'ra's act only had immediate effects on themself, Theo's effected her and everyone around her.