It was definitely not her being 'unconcerned', but her reaction to being overwhelmed. She still hadn't processed the whole situation. An unconcerned person wouldn't serve as a nurse by putting in danger her life once she understood. She was overwhelmed because all she believed in was a lie and she still didn't have a clear understanding about people's life as a person grown completely sheltered. She had to process things while feeling completely broken.
As for Heiner, he still refuses to see her for herself, and insists on the image he has created in his head about her, hence why people are hating. He's being frustrating. I definitely want both of them to heal but this doesn't mean they have to end up together. The ending of the novel felt very bittersweet to me.
Oh shit i think i misread the first part of your comment. You were referring to the first time they met? That still isn't being unconcerned but rather ignorant. She only knew war as a 'word' not what the repercussions really mean. She saw it as something that is necessary for peace. She still didn't really know what war is and what it means. Once again, she grew sheltered and only heard the versions of the story that were plausible to her father and her family.
NGL I feel we are not looking into Heiner’s life much. We all care about Annette, but what about him? Him loving her for a long time and then when he faced her, he came to know his oppressor is her father. Also not to forget Annette did say “she’s sorry for the people dying” in their first meeting in an unconcerned way. I’m not Villianizing her, Heiner loves her but the fact that him suffering and since being in such conditions, the self pitying, I feel we must stop hating on him? And wish for both of them healing and getting back together