Aura has been a really interesting case to observe. Reading the manga as it has come out, Aura was really just a minor character, never placing too highly in the popularity polls that they did prior to the anime’s release. It wasn’t really until the anime that her popularity took off. Her story was very faithfully adapted, so I don’t think there is much of a story difference that can be ascribed to causing the difference in reception.
I am guessing the root cause is some combination of a different audience as well as the effects of being a really fucking good adaptation. The Frieren adaptation has been stellar, and the conclusion of Aura’s fight is no different. In particular, I think the OST added a lot to the end of that episode, both in the lead up to Frieren’s command and the lack of OST immediately afterwards.



The linked reddit post says Agnes Digital.