@Yalu12 it’s a bit easier to understand in the novel. But basically it comes down to the fact that she was a literal sword for hundreds of years thousands of years and has a lot of PTSD from that. she never wanted to kill and she was used to murder a lot of people so she’s got a huge disconnect from even wanting to feel emotions.
As the prince starts to become more affectionate with her, she does notice it. she is aware. The novel spends more time when they’re younger and she spends a lot of time cultivating him—as creepy as that sounds—to be dependent on her and to seek her approval.
She knows he’s probably feeling something for her which is why she wants to get him his princess candidate, to reestablish a distance. Also another part is she’s completely using him—like he’s fine with it, but her whole intention of becoming his master is literally to destroy the kingdom to get her revenge for how she was treated, so she also can’t really allow herself to acknowledge his humanness or his softer side (be because that would kind of force her to realize she still has a human side)