I would have had chained Aura to a much worse fate -- make her turn on her own demon-kin and ruthlessly slaughter them all before making her kill herself. Frieren spoiled a good opportunity to have a useful pawn/spy. But I suppose it was probably for the best anyway since leaving a demon like...
Wow.. This thing is like a car wreck. I know I shouldn't look but I just can't resist.
You must see it through to the end. At least for uh... educational purposes. Yeah... That's it.