Oh? Is she actually believing that she can make her brother become a better person? That's... pretty incredible. Like, she knows about how her brother will betray and have her killed, how he used her and all, but still sympathizes with how he is a kid that still yearns for affection.
Honestly, I actually like her even more because of that. She's not a doormat that will let someone walk all over her, so if her brother does try to turn on her, she will likely kill him, as she's gained much strength and fortitude over her isekai, but she still believes in the possible chance to save her brother even now.