>>276821311It's not about her overcoming her nature, it's about her coming to terms with the fact that the people around her WILL die in what is the blink of an eye and making sure to make the most of that time. It was never that she didn't care, she just took for granted that people would be around later. Frieren never had to change her nature, she just had to adjust her perspective.
Demons straight up lack the capacity for empathy. It's not something they can overcome, much in the same way as a snake will never walk because it doesn't have legs.